- A
- abnormal termination
- (1) The cessation of processing prior to
planned termination. (T)
- (2) A system failure or operator action
that causes a job to end unsuccessfully.
- (3) In DB2, exits that are not under
program control, such as a trap or segv.
- access path
- The method that is selected by the
optimizer for retrieving data from a specific table. For example, an
access path can involve the use of an index, a sequential scan, or a
combination of the two.
- access plan
- The set of access paths that are
selected by the optimizer to evaluate a particular SQL statement. The
access plan specifies the order of operations to resolve the execution plan,
the implementation methods (such as JOIN), and the access path for each table
referenced in the statement.
- accounting string
- User-defined accounting
information that is sent to DRDA servers by DB2 Connect. This
information can be specified at one of these locations:
- The client workstation using the SQLESACT API or the DB2ACCOUNT
environment variable
- The DB2 Connect workstation using the DFT_ACCOUNT_STR database manager
configuration parameter.
- active log
- The subset of files consisting of
primary and secondary log files that are currently needed by the database
manager for crash recovery and rollback. Contrast with archive
log.
- adjacent nodes
- Two nodes connected together by at
least one path that connects no other nodes. (T)
- administrative authority
- A level of authority that gives a
user privileges over a set of objects. For example, DBADM authority
gives privileges over all objects in a database, and SYSADM authority gives
privileges over all objects in a system.
- ADSM
- ADSTAR Distributed Storage
Manager.
- ADSTAR Distributed Storage Manager (ADSM)
- A client/server product that
provides storage management and data access services in a heterogeneous
environment. It supports various communication methods, provides
administrative facilities to manage the backup and storage of files, and
provides facilities for scheduling backup operations.
- Advanced Peer-to-Peer Networking (APPN)
- An extension to SNA that features
greater distributed network control, dynamic definition of network resources,
and automated resource registration and directory lookup.
- Advanced Peer-to-Peer Networking (APPN) network
- A collection of interconnected
network nodes and their client end nodes. See also network node.
- Advanced program-to-program communication (APPC)
- The general facility that
characterizes the LU 6.2 architecture and its various implementations
in products.
- after-image
- The updated content of a source
table element that is recorded in a change data table or in a database log or
journal. Contrast with before-image.
- agent
- A separate process or thread that
carries out all DB2 requests that are made by a particular client
application.
- aggregate function
- Synonym for column function.
- alert
- An action, such as a beep or warning,
that is generated when a performance variable exceeds or falls below its
warning or alarm threshold.
- alias
- In DB2, an alternative name used to
identify a table, view, or database.
- alias chain
- A series of table aliases that
refer to each other in a sequential, non-repeating fashion.
- alphanumeric
- Pertaining to data that consists
of letters, digits, and usually other characters, such as punctuation
marks. (T) (A)
- ambiguous cursor
- A cursor that cannot be determined
to be updateable or read-only from its definition or context.
- API
- Application programming
interface.
- APPC
- Advanced program-to-program
communication.
- application ID
- A string that uniquely identifies an
application across networks. An ID is generated at the time that the
application connects to the database. This ID is known on both the
client and the server and can be used to correlate the two parts of the
application.
- application process
- The unit to which resources and
locks are allocated. An application process involves the running of one
or more programs.
- application programming interface (API)
- (1) A functional interface supplied by
the operating system or by a separately orderable licensed program. It
allows an application program written in a high-level language to use specific
data or functions of the operating system or the licensed programs.
- (2) In DB2, a function within the
interface. For example, the get error message API.
- application requester
- A facility that accepts a database
request from an application process and passes it to an application
server.
- application server
- The local or remote database
manager to which the application process is connected.
- Apply program
- A replication program that is used
to refresh or update a target table, depending on the applicable
source-to-target rules. Contrast with Capture program.
- Apply qualifier
- A character string that identifies
subscription definitions that are unique to each instance of the Apply
program.
- Apply trail table
- A replication source table at the
control server that records a history of the refreshes and updates performed
against target tables.
- APPN
- Advanced Peer-to-Peer
Networking.
- APPN network node
- Advanced Peer-to-Peer
Networking (APPN) network node. Synonymous with network node.
- archive log
- The set of log files that are
closed and are no longer needed for normal processing. These files are
retained for use in roll-forward recovery. Contrast with active
log.
- argument
- A value passed to or returned from a
function or procedure at run time.
- asynchronous
- Without regular time relationship;
unexpected and unpredictable with respect to the processing of program
instructions. Contrast with synchronous.
- asynchronous batched update
- A process in which all
changes to the source are recorded and applied to existing target data at
specified intervals. Contrast with asynchronous continuous
update.
- asynchronous continuous update
- A process in which all
changes to the source are recorded and applied to existing target data after
being committed in the base table. Contrast with asynchronous batched
update.
- attach
- In DB2, to remotely access objects
at the instance level.
- audit trail
- Data, in the form of a logical
path linking a sequence of events, used for tracing the transactions that have
affected the contents of a record. (T)
- authorization
- In computer security, the
right granted to a user to communicate with or make use of a computer
system. (T)
- authorization ID
- A character string in a statement
that designates a set of privileges. It is used by the database manager
for authorization checking and as an implicit qualifier for the names of
objects such as tables, views, and indexes.
- autocommit
- To automatically commit the
current unit of work after each SQL statement.
- automatic rebind
- A feature that automatically
rebinds an invalidated package without requiring a bind command to
be entered manually or a bind file to be present.
- auto-registration
- A process in which replica and
consistent change data tables are automatically defined as replication sources
at the target server.
- B
- backup pending
- The state of a database or
table space that prevents an operation from being performed until a backup is
made of the database or table space.
- base aggregate table
- A target table type that contains
data aggregated from a source table or a point-in-time table at
intervals.
- base table
- A table created with the CREATE
TABLE statement. Such a table has both its description and data
physically stored in the database. Contrast with view.
- basic conversation
- An LU 6.2 conversation
type between two transaction programs using the APPC basic conversation
API. Contrast with mapped conversation.
- basic predicate
- A predicate that compares two
values.
- before-image
- The content of a source table
element prior to a refresh or update, as recorded in a change data table, or
in a database log or journal. Contrast with after-image.
- binary large object (BLOB)
- A sequence of bytes, where the
size of the sequence ranges from 0 bytes to 2 gigabytes. This string
does not have an associated code page and character set. Image, audio,
and video objects are stored in BLOBs.
- bind
- In SQL, the process by which the
output from the SQL precompiler is converted to a usable structure called an
access plan. During this process, access paths to the data are selected
and some authorization checking is performed.
- bindery object name
- A 48-byte character string that
contains the name of a bindery object on the NetWare** file server. The
database manager configuration field, objectname, uniquely represents a DB2
server instance, and is stored as an object in the bindery on a NetWare file
server.
- bind file
- A file produced by the precompiler
when the bind command or API is used with the BINDFILE
option. This file includes information on all SQL statements in the
application program.
- bit data
- Data that is not associated with a
coded character set and is therefore never converted.
- BLOB
- Binary large object.
- block
- A string of data elements recorded or
transmitted as a unit.
- blocking
- An option that is specified when
binding an application. It allows caching of multiple rows of
information by the communications subsystem so that each FETCH statement does
not require the transmission of one row for each request across the
network.
- broadcast join
- A join in which all
partitions of a table are sent to all nodes.
- built-in function
- An SQL function that is
provided by DB2 and appears in the SYSIBM schema. Contrast with
user-defined function.
- byte reversal
- A technique in which numeric data
is stored with the least significant byte first.
- C
- cache
- A buffer that contains frequently
accessed instructions and data; it is used to reduce access time.
- Call Level Interface (CLI)
- A callable API for database access,
which is an alternative to an embedded SQL API. In contrast to embedded
SQL, CLI does not require precompiling or binding by the user, but instead
provides a standard set of functions to process SQL statements and related
services at run time.
- Capture program
- A replication program that reads
database log or journal records to capture data about changes made to source
tables. Contrast with Apply program.
- cardinality
- The number of rows in a
database table.
- cascade rejection
- The process of rejecting a
replication transaction because it is associated with a transaction that had a
conflict detected and was itself rejected.
- cast function
- A function used to convert
instances of a data type (origin) into instances of a different data type
(target). In general, cast functions have the name of the target data
type. They have one single argument whose type is the origin data type;
their return type is the target data type.
- catalog
- A set of tables and views
maintained by the database manager. These tables and views contain
information such as descriptions of tables, views, and packages.
- catalog node
- The node at which the catalog
tables reside. The catalog node can be a different node for each
database.
- CCSID
- Coded character set
identifier.
- CDRA
- Character Data Representation
Architecture.
- change aggregate table
- A type of target table that
contains data aggregations based on changes recorded for a source
table.
- change data (CD) table
- A replication control table
at the source server that contains changed data for a replication source
table. The Capture program populates the CD table by copying the
changes from the database log or journal. The contents of the CD table
are then copied by the Apply program to the target table.
- Character Data Representation Architecture (CDRA)
- An architecture used to achieve
consistent representation, processing, and interchange of string data.
- character large object (CLOB)
- A sequence of characters
(single-byte, multi-byte, or both) where the length can be up to 2
gigabytes. A data type that can be used to store large text
objects. Also called character large object string.
- character string
- A sequence of bytes or
characters.
- character string delimiter
- The characters used to
enclose character strings in delimited ASCII files that are imported or
exported. See delimiter.
- check condition
- A restricted form of search
condition used in check constraints.
- check constraint
- Specifies a check condition that
is not false for each row of the table on which the constraint has been
defined.
- check pending
- A state into which a table can be
put where only limited activity is allowed on the table and constraints are
not checked when the table is updated.
- circular log
- A database log in which records are
overwritten if they are no longer needed by an active database.
Consequently, if a failure occurs, lost data cannot be restored during forward
recovery. Contrast with recoverable log.
- CLI
- Call Level Interface.
- client
- Any program (or workstation it is
running on) that communicates with and accesses a database server.
- CLOB
- Character large object.
- CLP
- Command Line Processor.
- clustered index
- An index whose sequence of
key values closely corresponds to the sequence of rows stored in a
table. The degree to which this correspondence exists is measured by
statistics that are used by the optimizer.
- coded character set
- A set of unambiguous rules
that establishes a character set and the one-to-one relationships between the
characters of the set and their coded representations.
- coded character set identifier (CCSID)
- A number that includes an
encoding scheme identifier, character set identifiers, code page identifiers,
and other information that uniquely identifies the coded graphic character
representation.
- code page
- A set of assignments of characters
to code points.
- code point
- In CDRA, a unique bit pattern
that represents a character in a code page.
- code set
- Encoding values for a character set
that provides the interface between the system and its input and output
devices. ISO uses code set as the term equivalent to the IBM-defined
term code page.
- cold start
- A system start, using an initial
program load procedure. Contrast with warm start.
- collating sequence
- The sequence in which the
characters are ordered for the purpose of sorting, merging, comparing, and
processing indexed data sequentially.
- collocated join
- The result of two tables
being joined in which:
- The tables reside in a single-partition nodegroup in the same database
partition; or they are in the same partitioned nodegroup and have the same
number of partitioning columns, the columns are partition compatible, and both
tables use the same partitioning function.
- All pairs of the corresponding partitioning key columns participate in the
equijoin predicates.
- column distribution value
- Statistics describing the most
frequent values of some column or the quantile values. These values are
used in the optimizer to help determine the best access plan.
- column function
- An operation used in queries that
applies to the values from several rows. Column functions include SUM,
AVG, MIN, MAX, COUNT, STDDEV, and VARIANCE. Synonymous with aggregate
function.
- Command Line Processor (CLP)
- A character-based interface for
entering SQL statements and database manager commands.
- commit
- The operation that ends a unit of
work by releasing locks so that the database changes made by that unit of work
can be perceived by other processes. This operation makes the data
changes permanent.
- commit point
- A point in time when data is
considered to be consistent.
- common critical section table
- A replication control table at
the source server that is used to establish concurrency control between the
Capture and Apply programs and to prevent an update replication cycle.
- Common Programming Interface Communications (CPI-C)
- An API for applications that
require program-to-program communication, making use of SNA's LU
6.2 to create a set of interprogram services.
- common pruning control table
- A replication control table
at the source server that coordinates the pruning of the change data and
unit-of-work control tables. The values in this table indicate how much
data has been replicated by the Apply program and can be safely pruned by the
Capture program.
- common registrations table
- A replication control table
at the source server that relates each source table or view to an associated
change data table and consistent change data table, if applicable.
- common subscription columns table
- A replication control table
that contains column details of target tables.
- common subscription events table
- A replication control
table that defines the events that trigger replication, including the event
name and time.
- common subscription set table
- A replication control table
that defines the members of a subscription set including the set name, Apply
qualifier, source server, target server, and status.
- common subscription statements table
- A replication control
table used to store the optional SQL statements that can be run at the
beginning or end of the set subscription cycle.
- common subscription targets member table
- A replication control
table that maps the source and target table relationships within a
subscription set.
- common table expression
- An expression that defines a
result table with a name (qualified SQL identifier) that can be specified as a
table name in any FROM clause in the fullselect that follows the WITH
clause.
- comparison operator
- An infix operator used in
comparison expressions. Comparison operators are ¬< (not less
than), <= (less than or equal to), ¬= (not equal to), = (equal to),
>= (greater than or equal to), > (greater than), and ¬> (not greater
than).
- complete
- A table attribute indicating that
the table contains a row for every primary key value of interest. As a
result, a complete source table can be used to perform a refresh of a target
table.
- composite key
- A key composed of more than one
column from a database table.
- compound SQL statement
- A block of SQL statements that
are executed in a single call to the application server.
- concurrency
- The shared use of resources by
multiple interactive users or application processes at the same time.
- condensed
- A table attribute indicating that
the table contains current data rather than a history of changes to the
data. A condensed table includes no more than one row for each primary
key value in the table. As a result, a condensed table can be used to
supply current information for a refresh.
- conflict detection
- The process of detecting an
out-of-date row in a replica that was updated by a user application.
When a conflict is detected, the transaction that caused the conflict is
rejected. See also enhanced conflict detection, standard conflict
detection.
- connect
- In DB2, to access objects at the
database level.
- connection
- (1) An association between an
application process and an application server.
- (2) In data communications, an
association established between functional units for conveying
information.
- connection handle
- Within the CLI, the data
object that contains information associated with a connection. This
includes general status information, transaction status, and diagnostic
information.
- consistent change data (CCD) table
- A replication table that is used
for staging data, with four replication control columns. It can be one
of the following types:
- An internal CCD table that is a join of the change data table and the
unit-of-work table at the source server.
- A regular CCD table that is a copy of the internal CCD table on a remote
server.
- An external source table that is not a DB2 origin table; it is manually
updated with four replication columns and defined as a replication source
table.
- consolidation replication
- A replication model in which
the data from multiple source tables is replicated to a single target
table. Contrast with fan-out replication.
- constraint
- A rule that limits the values
that can be inserted, deleted, or updated in a table. See check
constraint, referential constraint, and unique constraint.
- container
- See table space container.
- contention
- In the database manager, a
situation in which a transaction attempts to lock a row or table that is
already locked.
- Control Center
- A graphical interface that
shows database objects (such as databases and tables) and their relationship
to each other. From the Control Center you can perform the tasks
provided by the DBA Utility, Visual Explain, and Performance Monitor
tools.
- control point
- (1) In APPN, a component of a
node that manages resources of that node and optionally provides services to
other nodes in the network. Examples are a system services control
point (SSCP) in a type 5 node, a physical unit control point (PUCP) in a type
4 node, a network node control point (NNCP) in a type 2.1 (T2.1)
network node, and an end node control point (ENCP) in a T2.1 end
node. An SSCP and an NNCP can provide services to other nodes.
- (2) A component of a
T2.1 node that manages the resources of that node. If the
T2.1 node is an APPN node, the control point is capable of engaging in
control point-to-control point sessions with other APPN nodes. If the
T2.1 node is a network node, the control point also provides services
to adjacent end nodes in the T2.1 network. See physical
unit.
- control privilege
- The authority to completely
control an object. This includes the authority to access, drop, or
alter an object, and the authority to extend or revoke privileges on the
object to other users.
- control server
- The database location of the
applicable subscription definitions and apply trail table.
- control table
- A table in which replication
source and subscription definitions or other replication control information
is stored.
- conversation
- In APPC, a connection between
two transaction programs over a logical unit-logical unit (LU-LU) session that
allows them to communicate with each other while processing a
transaction.
- conversational transaction
- In APPC, two or more programs
communicating using the services of logical units (LUs).
- conversation security
- In APPC, a process that allows
validation of a user ID or group ID and password before establishing a
connection.
- conversation security profile
- The set of user IDs or group
IDs and passwords that are used by APPC for conversation security.
- Coordinated Universal Time (UTC)
- Synonym for Greenwich Mean
Time.
- coordinating agent
- The agent that is spawned when a
request is received by the database manager from an application. It
remains associated with the application during the life of the
application. This agent coordinates subagents that work for the
application. See also subagent.
- coordinator node
- The node to which the application
originally connected and on which the coordinating agent resides.
- coordinator subsection
- The subsection of an
application that starts other subsections (if any) and returns results to the
application.
- copy table
- See target table.
- correlated reference
- Reference to a column of a
table that is outside of a subquery.
- correlated subquery
- A subquery that contains a
correlated reference to a column of a table that is outside of the
subquery.
- correlation name
- An identifier designating a
table or view within a single SQL statement. It can be defined in any
FROM clause or in the first clause of an UPDATE or DELETE statement.
- country code
- When accessing the database,
the country code of the application is used to determine the date and time
presentation (display and print) formats. It is also used with the code
page to determine the default collating sequence for the database.
- CP
- Control point.
- CPI-C
- Common Programming Interface
Communications.
- CPI-C side information profile
- In SNA, the profile that
specifies the conversation characteristics to use when allocating a
conversation with a remote transaction program. The profile is used by
local transaction programs that communicate through CPI Communications.
It specifies the partner LU name (the name of the connection profile that
contains the remote LU name), the mode name, and the remote transaction
program name.
- CP name
- Control point name. A
network-qualified name of a control point consisting of a network ID qualifier
identifying the network to which the control point node belongs.
- crash recovery
- The process of recovering from an
immediate failure.
- CS
- Cursor stability.
- current function path
- An ordered list of schema
names used in the resolution of unqualified references to functions and data
types. In dynamic SQL, the current function path is found in the
CURRENT FUNCTION PATH special register. In static SQL, it is defined in
the FUNCPATH option for PREP and BIND commands.
- cursor
- A named control structure used by an
application program to point to a specific row within some ordered set of
rows. The cursor is used to retrieve rows from a set. See also
unambiguous cursor, ambiguous cursor.
- cursor stability (CS)
- An isolation level that
locks any row accessed by a transaction of an application while the cursor is
positioned on the row. The lock remains in effect until the next row is
fetched or the transaction is terminated. If any data is changed in a
row, the lock is held until the change is committed to the database.
- D
- DARI
- Database Application Remote
Interface. Former term for stored procedure.
- data area
- A memory area used by a program to
hold information.
- database administrator (DBA)
- An individual responsible for the
design, development, operation, safeguarding, maintenance, and use of a
database. (T)
- Database Application Remote Interface (DARI)
- Former term for stored
procedure.
- database client
- A workstation used to access a
database residing on a database server.
- database connection services (DCS) directory
- A directory that contains
entries for remote databases and the corresponding application requester used
to access them.
- database directory
- A directory that contains
database access information for all databases to which a client can
connect.
- database engine
- The part of the database manager
providing the base functions and configuration files needed to use the
database.
- database log
- A set of primary and secondary log
files consisting of log records that record all changes to a database.
The database log is used to roll back changes for units of work that are not
committed and to recover a database to a consistent state. See also
primary log, secondary log.
- database managed space (DMS) table space
- A table space whose space is
managed by the database. Contrast with system managed space (SMS) table
space.
- database management system (DBMS)
- Synonym for database
manager.
- database manager
- A computer program that manages
data by providing the services of centralized control, data independence, and
complex physical structures for efficient access, integrity, recovery,
concurrency control, privacy, and security.
- database manager instance
- A logical database manager
environment similar to an image of the actual database manager
environment. You can have several instances of the database manager
product on the same workstation. You can use these instances to
separate the development environment from the production environment, tune the
database manager to a particular environment, and protect sensitive
information from a particular group of people.
- database object
- Anything that can be created or
manipulated with SQL--for example, tables, views, indexes, packages,
triggers, or table spaces.
- database partition
- A part of the database that
consists of its own user data, indexes, configuration files, and transaction
logs. Sometimes called a node or database node.
- database server
- A functional unit that provides
database services for databases.
- database system monitor
- A collection of programming
APIs that monitor performance and status information about the database
manager, databases, and applications using the database manager and DB2
Connect.
- data definition language (DDL)
- A language for describing data
and its relationships in a database. Synonymous with data description
language. (T)
- data description language
- Synonym for data definition
language. (T)
- data enhancement
- The modification of data as
it is copied between the base table and the target table, including:
- Subsetting of data
- Generating multiple copies of data
- Converting data, such as code translation and value substitution
- Combining data in base tables
- Producing sums or averages of data
- DataJoiner
- A separately available product
that provides client applications integrated access to distributed data and
provides a single database image of a heterogeneous environment. With
DataJoiner, a client application can join data that is distributed across
multiple database management systems (using a single SQL statement) or update
a single remote data source, as if the data were local.
- data link control (DLC)
- In SNA, the protocol layer
that consists of the link stations that schedule data transfer over a link
between two nodes and perform error control for the link.
- data manipulation language (DML)
- A subset of SQL statements used to
manipulate data.
- date
- A three-part value that designates a
day, month, and year.
- date duration
- A DECIMAL(8,0) value that
represents a number of years, months, and days.
- datetime value
- A value of the data type
DATE, TIME, or TIMESTAMP.
- DB2 CLI
- DB2 Call Level Interface. An
alternative SQL interface for the DB2 family of products that takes full
advantage of DB2 capability.
- DB2 Connect
- A product that provides the
function necessary (DRDA application requester support) for client
applications to read and update data stored in DRDA application servers, such
as other members of the DB2 family.
- DB2 SDK
- DB2 Software Developer's
Kit.
- DB2 Software Developer's Kit (DB2 SDK)
- A collection of tools that help
developers create database applications.
- DB2UEXIT
- An optional, user-written
executable program that the database manager invokes to move or retrieve
archive log files.
- DBA
- Database administrator.
- DBA Utility
- A tool that lets DB2 users
configure databases and database manager instances, manage the directories
necessary for accessing local and remote databases, back up and recover
databases or table spaces, and manage media on a system using a graphical
interface. The tasks provided by this tool can be accessed from the
Control Center.
- DBCLOB
- Double-byte character large
object.
- DBCS
- Double-byte character set.
- DBMS
- Database management system.
- DBMS instance connection
- A logical connection
between an application and an agent process or thread owned by a DB2
instance.
- DCE**
- Distributed Computing
Environment.
- DDL
- Data definition language.
- deadlock
- A condition under which a
transaction cannot proceed because it is dependent on exclusive resources that
are locked by some other transaction, which in turn is dependent on exclusive
resources in use by the original transaction.
- deadlock detector
- A process within the
database manager that monitors the states of the locks to determine if a
deadlock condition has occurred. When a deadlock condition is detected,
the detector stops one of the transactions involved in the deadlock.
This transaction is rolled back and the other transactions proceed.
- delete rule
- A rule associated with a
referential constraint that either restricts the deletion of a parent row or
specifies the effect of such a deletion on the dependent rows.
- delimited identifier
- A sequence of characters
enclosed within quotation marks ("). The sequence must consist of a
letter followed by zero or more characters, each of which is a letter, digit,
or the underscore character.
- delimiter
- A character or flag that groups
or separates items of data.
- delimiter token
- A string constant, a
delimited identifier, an operator symbol, or any of the special characters
shown in syntax diagrams.
- dependent logical unit (DLU)
- An LU that requires assistance from
a system services control point (SSCP) to instantiate an LU-LU session.
- dependent row
- A row containing a foreign key that
matches the value of a parent key in the parent row. The foreign key
value thus represents a reference from the dependent row to the parent
row.
- dependent table
- A table that is a dependent in at
least one referential constraint.
- descendent row
- A row that is dependent on
another row or a row that is a descendent of a dependent row.
- descendent table
- A table that is a dependent
of another table or a descendent of a dependent table.
- deterministic function
- See not-variant
function.
- device name
- A name reserved by the system,
or a device driver that refers to a specific device.
- directed join
- A relational operation in
which all of the rows in one or both of the joined tables are rehashed and
directed to new database partitions based on the join predicate. If all
of the partitioning key columns in a table participate in the equijoin
predicates, the other table is rehashed; otherwise (if there is at least one
equijoin predicate), both tables are rehashed.
- directory services
- A portion of the APPN protocols
that maintains information about the location of resources in an APPN
network.
- distinct type
- A user-defined data type that
is internally represented as an existing type (its source type), but is
considered to be a separate and incompatible type for semantic
purposes.
- Distributed Computing Environment (DCE**)
- A set of services and tools that
support the creation, use, and maintenance of distributed applications in a
heterogeneous computing environment. DCE is independent of the
operating system and network; it provides interoperability and portability
across heterogeneous platforms.
- distributed directory database
- The complete listing of all
the resources in the network as maintained in the individual directories
scattered throughout an APPN network. Each node has a piece of the
complete directory, but it is not necessary for any one node to have the
entire list. Entries are created, modified, and deleted through system
definition, operator action, automatic registration, and ongoing network
search procedures. Synonymous with distributed network
directory.
- distributed network directory
- Synonym for distributed
directory database.
- distributed relational database
- A database whose tables are
stored on different but interconnected computing systems.
- Distributed Relational Database Architecture (DRDA)
- Architecture that defines formats
and protocols for providing transparent access to remote data. DRDA
defines two types of functions, the application requester function and the
application server function.
- distributed unit of work (DUOW)
- A unit of work that allows SQL
statements to be submitted to multiple relational database management systems,
but no more than one system per SQL statement.
- DLC
- Data link control.
- DLU
- Dependent logical unit.
- DML
- Data manipulation language.
- DMS table space
- Database managed space table
space.
- DNS
- Domain name system.
- Domain Name
- A mechanism, in TCP/IP, that
tracks the host names in a network. A domain name consists of a
sequence of names separated by dots.
- Domain Name System
- The distributed database
system used by TCP/IP to map human-readable machine names into IP
addresses.
- double-byte character large object (DBCLOB)
- A sequence of double-byte
characters, where the size can be up to 2 gigabytes. A data type that
can be used to store large double-byte text objects. Also called
double-byte character large object string. Such a string always has an
associated code page.
- double-byte character set (DBCS)
- A set of characters in which each
character is represented by two bytes.
- DRDA
- Distributed Relational Database
Architecture.
- DUOW
- Distributed unit of work.
- dynamic SQL
- SQL statements that are prepared
and run within a running program. In dynamic SQL, the SQL source is
contained in host language variables rather than being coded into the
program. The SQL statement might change several times while the program
is running.
- E
- EBCDIC
- Extended binary-coded decimal
interchange code. A coded character set of 256 8-bit characters.
- embedded SQL
- SQL statements coded within an
application program. See static SQL.
- EN
- End node.
- encoding scheme
- A set of rules to represent
character data.
- end node (EN)
- In APPN, a node that supports
sessions between its local control point (CP) and the CP in an adjacent
network node.
- enhanced conflict detection
- Conflict detection that
guarantees data integrity among all replicas and the origin table. The
Apply program locks all replicas in the subscription set against further
transactions, and begins detection after all changes made prior to locking
have been captured. See also standard conflict detection, conflict
detection.
- environment handle
- A handle that identifies the
global context for database access. All data that is pertinent to all
objects in the environment is associated with this handle.
- equijoin
- A join in which the predicate
contains an equals operator. For example, T1.C1 =
T2.C2.
- EUC
- Extended UNIX code.
- event monitor
- A database object for monitoring
and collecting data on database activities over a period of time.
- exclusive lock
- A lock that prevents
concurrently executing application processes from accessing database
data.
- executable statement
- An SQL statement that
can be embedded in an application program, dynamically prepared and executed,
or issued interactively.
- explain
- To capture detailed information
about the access plan that was chosen by the SQL compiler to resolve an SQL
statement. The information describes the decision criteria used to
choose the access plan.
- explainable statement
- An SQL statement for
which the explain operation can be performed. Explainable statements
are SELECT, UPDATE, INSERT, DELETE, and VALUES.
- explained statement
- An SQL statement for
which an explain operation was performed.
- explained statistics
- Statistics for a database
object that was referenced in an SQL statement at the time the statement was
explained.
- explain snapshot
- A capture of the current
internal representation of an SQL query and related information. This
information is required by the Visual Explain tool.
- export
- To copy data from database manager
tables to a file using formats such as PC/IXF, DEL, WSF, or ASC.
Contrast with import.
- exposed name
- A correlation name, a table, or
a view name specified in a FROM clause for which a correlation name is not
specified.
- Extended UNIX Code (EUC)
- A protocol that can support sets of
characters from 1 to 4 bytes in length. EUC is a means of specifying a
collection of code pages rather than actually being a code page encoding
scheme itself. This is the UNIX alternative to the PC double-byte
(DBCS) code page encoding schemes.
- extent
- An allocation of space, within a
container of a table space, to a single database object. This
allocation consists of multiple pages.
- extent map
- A meta-data structure stored
within a table space that records the allocation of extents to each object in
the table space.
- external source table
- A non-DB2 table that is
manually updated to match the consistent change data table structure and
defined as a replication source. See also consistent change data (CCD)
table.
- F
- fan-out replication
- A replication model in which data
from one source table is copied to multiple target tables, thereby
distributing the data to multiple locations. Contrast with
consolidation replication.
- fast communication manager (FCM)
- A group of functions that
provide internodal communication support.
- fenced
- A type of user-defined function or
stored procedure that is defined to protect the DBMS from modifications by the
function. The DBMS is isolated from the function or stored procedure by
a barrier. Contrast with not-fenced.
- file reference variable
- A host variable that is used to
indicate that data resides in a file on the client rather than in a client
memory buffer.
- file server
- A workstation that runs the
NetWare** operating system software and acts as a network server. DB2
uses the file server to store DB2 server address information, which a DB2
client retrieves to establish an IPX**/SPX client-server connection.
- filter
- A device or program that separates
data, signals, or material in accordance with specified criteria. (A)
- First Failure Service Log
- A file (db2diag.log) that
contains diagnostic messages, diagnostic data, alert information, and related
dump information. This file is used by database administrators.
- fixed-length string
- A character or graphic
string whose length is specified and cannot be changed. Contrast with
varying-length string.
- flagger
- A precompiler option that
identifies SQL statements in applications that do not conform to selected
validation criteria (for example, the ISO/ANSI SQL92 Entry level
standard).
- foreign key
- A key that is part of the
definition of a referential constraint and that consists of one or more
columns of a dependent table.
- foreign update
- An update that was applied to
a target table and replicated to the local table.
- forward recovery
- A process used to roll
forward a database or table space. It allows a restored database or
table space to be rebuilt to a specified point in time by applying the changes
recorded in the database log.
- fullselect
- A subselect, a values-clause, or
a number of both that are combined by set operators.
- fully qualified LU name
- See network-qualified
name.
- function
- A mapping, embodied as a program
(the function body), invocable by means of zero or more input values
(arguments) to a single value (the result).
- function body
- The piece of code that
implements a function.
- function family
- A set of functions with the
same function name. The context determines whether the usage refers to
a set of functions within a particular schema, or all the relevant functions
with the same name within the current function path.
- function invocation
- The use of a function
together with any argument values being passed to the function body.
The function is invoked by its name.
- function path
- An ordered list of schema
names that restricts the search scope for unqualified function invocations and
provides a final arbiter for the function selection process.
- function path family
- All the functions of the
given name in all the schemas identified (or used by default) in the
user's function path.
- function resolution
- The process, internal to the
DBMS, for which a particular function instance is selected for
invocation. The function name, the data types of the arguments, and the
function path are used to make the selection. Synonymous with function
selection.
- function selection
- Synonym for function
resolution.
- function shipping
- The shipping of the
subsections of a request to the specific node that contains the applicable
data.
- function signature
- The logical concatenation of
a fully qualified function name with the data types of all of its
parameters. Each function in a schema must have a unique
signature.
- G
- gap
- A situation in which the Capture
program is not able to read a range of log or journal records and there is
potential loss of change data.
- global table lock
- A table lock that is
acquired on all nodes in a table's nodegroup.
- global transaction
- A unit of work in a
distributed transaction processing environment in which multiple resource
managers are required.
- grant
- To give a privilege or authority to
an authorization ID.
- graphic character
- Synonym for DBCS
character.
- graphic string
- A sequence of DBCS
characters.
- group
- A logical organization of users that
have IDs according to activity or resource access authority.
- H
- handle
- A variable that represents an
internal structure within a software system.
- hash partitioning
- A partitioning strategy in which a
hash function is applied to the partitioning key value to determine the
database partition to which the row is assigned.
- hop
- In APPN, a portion of a route that has
no intermediate nodes. A hop consists of only a single transmission
group connecting adjacent nodes.
- host computer
- (1) In a computer network, a computer
providing services such as computation, database access, and network control
functions.
- (2) The primary or controlling
computer in a multiple computer installation.
- host identifier
- A name declared in the host
program.
- host language
- Any programming language in which
you can embed SQL statements.
- host node
- In SNA, a subarea node that
contains a system services control point (SSCP); for example, an IBM
System/390 computer with MVS and VTAM.
- host program
- A program written in a host
language that contains embedded SQL statements.
- host variable
- In an application host program, a
variable referenced by embedded SQL statements. Host variables are
programming variables in the application program and are the primary mechanism
for transmitting data between tables in the database and application program
work areas.
- I
- identifier
- One or more characters used to
identify or name a data element and possibly to indicate certain properties of
that data element. (A)
- ILU
- Independent logical unit.
- import
- To copy data from an external file,
using formats such as PC/IXF, DEL, WSF or ASC, into database manager
tables. Contrast with export.
- import utility
- Transactional utility that inserts
user-supplied record data into a table.
- independent logical unit (ILU)
- An LU that is able to activate
an LU-LU session without assistance from a system services control point
(SSCP). It does not have an SSCP-LU session. Contrast with
dependent logical unit.
- index
- A set of pointers that are logically
ordered by the values of a key. Indexes provide quick access to data
and can enforce uniqueness on the rows in the table.
- index key
- The set of columns in a table used
to determine the order of index entries.
- index partition
- The part of an index that is
associated with a table partition at a given node. An index defined on
a table is implemented by multiple index partitions, one per table
partition.
- index sargable predicates
- Predicates that are applied
to index entries, in index leaf pages, to reduce the number of index entries
that qualify the SQL request. This helps reduce the number of data rows
accessed.
- indicator variable
- A variable used to represent
the null value in an application program. If the value for the selected
column is null, a negative value is placed in the indicator variable.
- indoubt transaction
- Pertains to a transaction in
which one phase of a two-phase commit completes successfully but the system
fails before a subsequent phase can complete.
- initialization fullselect
- The first fullselect
in a recursive common table expression that gets the direct children of the
initial value from the source table.
- inner join
- A join method in which a column
that is not common to all of the tables being joined is dropped from the
resultant table. Contrast with outer join.
- inoperative package
- A package that cannot be
used because one or more functions that it depends on have been
dropped. Such a package must be explicitly rebound. Contrast
with invalid package.
- inoperative trigger
- A trigger that is no
longer usable. A trigger will be marked inoperative when an object on
which it depends is dropped (or made inoperative) or a privilege on which it
depends is revoked.
- inoperative view
- A view that is no longer
usable. A view will be marked as inoperative when either:
- SELECT privilege on a table or view that the view is dependent on is
revoked from the definer of the view.
- An object on which the view definition is dependent was dropped (or
possibly made inoperative in the case of another view).
- insert rule
- A condition enforced by the
database manager that must be met before a row can be inserted into a
table.
- instance
- See database manager
instance.
- intermediate network node
- In APPN, a node that is
part of a route between an origin LU (OLU) and a destination LU (DLU) but that
neither contains the OLU or the DLU nor serves as the network server for
either the OLU or DLU.
- internal CCD table
- A consistent change data
table that is a join of the change data table and the unit-of-work table at
the source server.
- Internet Protocol (IP)
- A protocol used to route
data from its source to its destination in an Internet environment.
- Internetwork Packet Exchange** (IPX**)
- A connectionless datagram protocol,
used in a NetWare** LAN environment, to transfer data to a remote node.
IPX makes a best-effort attempt to send data packets, but does not guarantee
reliable delivery of the data.
- inter-partition parallelism
- Refers to the ability to
perform multiple database operations (such as index creation, database load,
and SQL queries) at the same time across multiple partitions of a partitioned
database. Contrast with intra-partition parallelism.
- Inter-Process Communication (IPC)
- A mechanism of an operating system
that allows processes to communicate with each other.
- intra-partition parallelism
- Refers to the ability to
perform multiple database operations (such as index creation, database load,
SQL queries) at the same time within a single database partition.
Contrast with inter-partition parallelism.
- intra-query parallelism
- Processing parts of a single
query at the same time using either intra-partition parallelism,
inter-partition parallelism, or both.
- invalid package
- A package that becomes invalid
when an object that the package depends on is dropped. (The object is
of a type other than function; for example, index.) Such a package is
implicitly rebound upon invocation. Contrast with inoperative
package.
- I/O parallelism
- See parallel I/O.
- IP
- Internet Protocol.
- IPX**
- Internetwork Packet
Exchange**.
- isolation level
- An attribute that defines
the degree to which an application process is isolated from other concurrently
executing application processes.
- J
- job scheduler
- A program used to automate
certain tasks for running and managing database jobs.
- join
- A relational operation that allows for
retrieval of data from two or more tables based on matching column
values.
- K
- key
- A column or an ordered collection of
columns that are identified in the description of a table, index, or
referential constraint.
- key-value based partitioning strategy
- A strategy for
assigning rows in a table to database partitions. Rows are assigned
based on the values of the partitioning key columns.
- keyword
- One of the predefined words of a
computer, command language, or an application.
- L
- labeled duration
- A number that represents a
duration of years, months, days, hours, minutes, seconds, or
microseconds.
- large object (LOB)
- A sequence of bytes, where the
length can be up to 2 gigabytes. It can be any of three types:
BLOB (binary), CLOB (single-byte character or mixed) or DBCLOB (double-byte
character).
- length attribute
- A value associated with a string
that represents the declared fixed length or maximum length of the
string.
- LEN node
- Low-entry networking node.
- list prefetch
- An access method that takes
advantage of prefetching even in queries that do not access data
sequentially. This is done by scanning the index and collecting RIDs in
advance of accessing any data pages. These RIDs are then sorted, and
data is prefetched using this list.
- load copy
- A backup image of data that was
loaded at a previous time and can be restored during roll-forward
recovery.
- load utility
- A nontransactional utility that
performs block updates of table data. Contrast with import
utility.
- LOB
- Large object.
- LOB locator
- A mechanism that allows an
application program to manipulate a large object value in the database
system. A LOB locator is a simple token value that represents a single
LOB value. An application program retrieves a LOB locator into a host
variable and can then apply SQL functions to the associated LOB value via the
locator.
- local database
- A database that is physically
located on the workstation in use. Contrast with remote
database.
- local database directory
- A directory where a database
physically resides. Databases that are displayed in the local database
directory are located on the same node as the system database
directory.
- local table lock
- A table lock that is
acquired only on a single database partition.
- local update
- An update to the base table,
not to the replica.
- locator
- See LOB locator.
- lock
- (1) A means of serializing events or
access to data.
- (2) A means of preventing uncommitted
changes made by one application process from being perceived by another
application process and for preventing one application process from updating
data that is being accessed by another process.
- lock escalation
- In the database manager, the
response that occurs when the number of locks issued for one agent exceeds the
limit specified in the database configuration; the limit is defined by the
MAXLOCKS configuration parameter. During a lock escalation, locks are
freed by converting locks on rows of a table into one lock on a table.
This is repeated until the limit is no longer exceeded.
- locking
- The mechanism used by the database
manager to ensure the integrity of data. Locking prevents concurrent
users from accessing inconsistent data.
- log
- (1) See database log.
- (2) A file used to record changes made in a
system.
- log head
- The oldest written log record in
the active log.
- logical node
- A node on a processor when more
than one node is assigned to that processor. See also node.
- logical operator
- A keyword that specifies
how multiple search conditions are to be evaluated (AND, OR) or if the logical
sense of a search condition is to be inverted (NOT).
- logical unit (LU)
- In SNA, a port through which an
end user accesses the SNA network to communicate with another end user.
An LU may be capable of supporting many sessions with other LUs.
- logical unit 6.2 (LU 6.2)
- The LU type that supports
sessions between two applications using APPC.
- log partition
- The log file on each database
partition that records database activity for that database partition.
- log record
- A record of an update to a
database performed during a unit of work. This record is written after
the log tail of the active log.
- log tail
- The log record that was written
most recently in an active log.
- long string
- A varying-length string whose
maximum length is greater than 254 bytes.
- long table space
- A table space that can store only long
string or large object (LOB) data.
- low-entry networking node (LEN node)
- A type 2.1 node
that supports independent LU protocols but does not support CP-CP
sessions. It can be a peripheral node attached to a boundary node in a
subarea network, an end node attached to an APPN network node in an APPN
network, or a peer-connected node directly attached to another LEN node or
APPN end node.
- LU
- Logical unit.
- LU 6.2
- See logical unit 6.2.
- LU type
- The classification of a logical unit
in terms of the specific subset of SNA protocols and options it supports for a
given session, specifically:
- The values allowed in the session activation request
- The usage of data stream controls, function management headers, request
unit parameters, and sense data values
- Presentation services protocols such as those associated with function
management headers
- M
- mapped conversation
- In APPC, a conversation
between two transaction programs (TPs) using the APPC mapped conversation
API. In typical situations, end-user TPs use mapped conversation and
service TPs use basic conversations. However, either type of program
can use either type of conversation. Contrast with basic
conversation.
- masking character
- A character used to represent
optional characters at the front, middle, and end of a search term.
Masking characters are normally used for finding variations of a term in a
precise index.
- MBCS
- Multi-byte character set.
- migration
- (1) The process of moving data from
one computer system to another without converting the data.
- (2) Installation of a new version or
release of a program to replace an earlier version or release.
- mixed-character string
- A string containing a
mixture of single-byte and multi-byte characters.
- mixed-data string
- Synonym for mixed-character
string.
- mobile client
- The node, usually a lap top
computer, where the mobile enabler and replication source and target tables
used in a mobile environment are located. The mobile replication mode
is invoked from the mobile client.
- mobile replication enabler
- A replication program that
starts the mobile replication mode at the mobile client.
- mobile replication mode
- A mode of replication in
which the Capture and Apply programs operate as needed rather than
autonomously and continuously. This mode is invoked from the mobile
client and allows data to be replicated when the mobile client is available
for a connection to the source or target server.
- modelled statistics
- Statistics for a database
object that may or may not be referenced in an SQL statement, yet currently
exist in an explain model. The object may or may not currently exist in
the database.
- mode name
- In APPC, the name used by the
initiator of a session to designate the characteristics desired for the
session, such as message length limits, sync point, class of service within
the transport network, and session routing and delay characteristics.
- monitoring session
- The act of monitoring a
database manager or of playing back information from a previously monitored
database manager. The DB2 Performance Monitor is used for creating a
monitoring session and for selecting which database objects to monitor.
- monitor switch
- Database manager parameters
manipulated by the user to control the type of information and the quantity of
information returned in performance snapshots.
- multi-byte character set (MBCS)
- A set of characters in which each
character is represented by two or more bytes. Those using only two
bytes are more commonly known as double-byte character sets.
- multitasking
- A mode of operation that
provides for concurrent performance, or interleaved execution of two or more
tasks. (I) (A)
- N
- NAU
- Network addressable unit.
- NDS
- Network Directory Services.
- nested table expression
- A result table obtained
directly or indirectly from one or more other tables through the evaluation of
a fullselect that is specified in the FROM clause.
- NETID
- Network identifier. Synonym
for network name.
- network address
- An identifier for a node in
a network.
- network addressable unit (NAU)
- A logical unit (LU), physical unit
(PU), control point (CP), or system services control point (SSCP). It
is the origin or the destination of information transmitted by the path
control network. See also network name.
- Network Directory Services (NDS)
- A global, distributed, replicated
database introduced in NetWare** Version 4.0 that maintains information
about, and provides access to, every resource on the network. The
NetWare Directory database organizes objects, independent of their physical
location, in a hierarchical tree structure called the directory tree.
- network name
- In SNA, a symbolic name by
which end users refer to a network addressable unit (NAU), a link station, or
a link. Synonymous with NETID.
- network node (NN)
- In APPN, a node on the network that
provides distributed directory services, topology database exchanges with
other APPN network nodes, and session and routing services. Synonym for
APPN network node.
- network node server
- An APPN network node that
provides network services for its local logical units and adjacent end
nodes.
- network-qualified name
- The name by which an
LU is known throughout an interconnected SNA network. A
network-qualified name consists of a network name identifying the individual
subnetwork, and a network LU name. Network-qualified names are unique
throughout an interconnected network. Also known as the
network-qualified LU name, or fully qualified LU name.
- network services
- The services within network
addressable units that control network operation through SSCP-SSCP, SSCP-PU,
SSCP-LU, and CP-CP sessions.
- NN
- Network node.
- node
- (1) In database partitioning, synonymous
with database partition.
- (2) In hardware, a uniprocessor or
symmetric multiprocessor (SMP) computer that is part of a clustered system or
a massively parallel processing (MPP) system. For example, RS/6000 SP
is an MPP system that consists of a number of nodes connected by a high-speed
network.
- (3) In communications, an end point of a
communications link, or a junction common to two or more links in a
network. Nodes can be processors, communication controllers, cluster
controllers, terminals, or workstations. Nodes can vary in routing and
other functional capabilities.
- node directory
- A directory that contains
information necessary to establish communications from a client workstation to
all applicable database servers.
- nodegroup
- A named group of one or more
database partitions.
- noncondensed attribute
- A table attribute
indicating that the table contains a history of changes to the data, not
current data. A table that has this attribute set includes more than
one row for each key value.
- nondelimited ASCII (ASC) format
- A file format used
to import data. Nondelimited ASCII is a sequential ASCII file with row
delimiters used for data exchange with any ASCII product.
- normalization
- In databases, the process of
restructuring a data model by reducing its relations to their simplest
forms. (T)
- not-fenced
- A type of user-defined function
or stored procedure that is defined to be run in the DBMS process.
Contrast with fenced.
- not-variant function
- A user-defined function
whose result is solely dependent on the values of the input arguments.
Successive invocations with the same argument values always produce the same
results. Contrast with variant function.
- nullable
- The condition where a value for a
column, function parameter, or result can have an absence of a value.
For example, a field for a person's middle initial does not require a
value.
- null value
- A parameter position for which no
value is specified.
- O
- object
- (1) Anything that can be created or
manipulated with SQL--for example, tables, views, indexes, or
packages.
- (2) In object-oriented design or
programming, an abstraction consisting of data and operations associated with
that data.
- (3) For NetWare**, an entity that is
defined on the network and thus given access to the file server.
- object property
- A property that identifies a
category of information associated with an object. A NetWare** bindery
object can be assigned one or more properties. The DB2 server instance
object has an object property NET_ADDR, which denotes the location of the
record within the object.
- object type
- (1) A 2-byte number that classifies
an object in the bindery on a NetWare** file server. 062B represents
the DB2 database server object type.
- (2) A categorization or grouping of
object instances that share similar behaviors and characteristics.
- ODBC
- Open Database Connectivity.
- ODBC driver
- A driver that implements ODBC
function calls and interacts with a data source.
- offline backup
- A backup of the database or
table space that was made when the database or table space was not being
accessed by applications. The Backup Database utility acquires
exclusive use of the database until the backup is complete. Contrast
with online backup.
- offline restore
- A restoration of a copy of a
database or table space from a backup. The Backup Database utility has
exclusive use of the database until the restore is completed.
- online backup
- A backup of the database or
table space that is made while the database or table space is being accessed
by other applications. Contrast with offline backup.
- online monitor
- See Snapshot Monitor.
- online restore
- A restoration of a copy of a
database or table space while the database or table space is being accessed by
other applications. Contrast with offline restore.
- Open Database Connectivity (ODBC)
- An API that allows access to
database management systems using callable SQL, which does not require the use
of a SQL preprocessor. The ODBC architecture allows users to add
modules, called database drivers, that link the application to their choice of
database management systems at run time. Applications do not have to be
linked directly to the modules of all the supported database management
systems.
- operand
- An entity on which an operation is
performed.
- optimized SQL text
- SQL text, produced by the
Explain facility, based on the query actually used by the optimizer to choose
the access plan. This query has been supplemented and rewritten by the
various components of the SQL compiler during statement compilation.
The text has been reconstructed from its internal representation, and differs
from the original SQL text. The optimized statement produces the same
result as the original statement.
- optimizer
- A component of the SQL compiler
that chooses an access plan for a DML statement by modelling the execution
cost of many alternative access plans and choosing the one with the minimal
estimated cost.
- ordinary identifier
- In SQL, a letter, which
might be followed by zero or more characters, each of which is a letter (a-z
and A-Z), a symbol, a number, or the underscore character, used to form a
name.
- ordinary token
- A numeric constant, an
ordinary identifier, a host identifier, or a keyword.
- outer join
- A join method in which a column
that is not common to all of the tables being joined becomes part of the
resultant table. Contrast with inner join.
- output file
- A database or device file that
is opened with the option to allow the writing of records.
- overflow record
- (1) On an indirectly addressed file, a
record whose key is randomized to the address of a full track or to the
address of a home record.
- (2) In DB2, an updated record that is
too large to fit on the page it is currently stored in. The record is
copied to a different page and its original location is replaced with a
pointer to the new location.
- (3) In Database Monitor, a record
inserted in the event monitor data stream to indicate that records were
discarded because the named pipe was full and records were not processed in
time. An overflow record indicates how many records were
discarded.
- overloaded function name
- A function name for
which there are multiple functions within a function path or schema.
Those within the same schema must have different signatures.
- P
- package
- A control structure produced during
program preparation that is used to execute SQL statements.
- packet
- In data communication, a sequence of
binary digits, including data and control signals, that is transmitted and
switched as a composite whole.
- page
- A block of storage within a table or
index whose size is 4096 bytes (4 K).
- parallel I/O
- Refers to the process of reading
from or writing to two or more I/O devices at the same time to reduce response
time.
- parallelism
- The ability to perform multiple
database operations at the same time (in parallel). See inter-partition
parallelism, intra-partition parallelism, and parallel I/O.
- parallel session
- In SNA, two or more
concurrently active sessions between the same two logical units (LUs).
Each session can have different session parameters. Contrast with
session.
- parameterized data type
- A data type that can
be defined with a specific length, scale, or precision. These are the
string and decimal data types.
- parameter marker
- A question mark (?) that
appears in a statement string of a dynamic SQL statement. The question
mark can appear where a host variable could appear if the statement string was
a static SQL statement.
- parent key
- A primary key or unique key that
is used in a referential constraint. The values of a parent key
determine the valid values of the foreign key in the constraint.
- parent row
- A row that has at least one
dependent row.
- parent table
- A table that is a parent in at
least one referential constraint.
- partition compatible join
- A join where all of the
rows that are joined reside in the same database partition.
- partitioned database
- A database with two or more database partitions. Data in user
tables can be located in one or more database partitions. When a table
is on multiple partitions, some of its rows are stored in one partition and
others are stored in other partitions. See database partition.
- partitioning function
- A function that takes a
partitioning key value of a row as input and produces a partition number as
output.
- partitioning key
- (1) An ordered set of one or
more columns in a given table. For each row in the table, the values in
the partitioning key columns are used to determine on which database partition
the row belongs.
- (2) In replication, an ordered
set of one or more columns in a given table. For each row in the source
table, the values in the partitioning key columns are used to determine in
which target table the row belongs.
- partitioning map
- A vector of partition
numbers that maps a partitioning map index to database partitions in the
nodegroup.
- partitioning map index
- A number assigned to a hash
partition or range partition.
- partner logical unit (LU)
- In SNA, the remote participant in
a session.
- peer-to-peer communication
- Communication between two SNA
logical units (LUs) that is not managed by a host; commonly used when
referring to LU 6.2 nodes.
- performance metrics
- A collection of all performance
variables belonging to the same database object.
- Performance Monitor
- A tool that lets database
administrators use a graphical interface to monitor the performance of a DB2
system for tuning purposes. The tasks provided by this tool can be
accessed from the Control Center.
- performance snapshot
- Performance data for a set of
database objects that is retrieved from the database manager at a point in
time.
- performance variable
- A statistic derived from
performance data obtained from the database manager. The expression for
this variable can be user-defined.
- performance variable profile
- A flat file that
contains definitions of performance variables. This file can be edited,
copied, and shared. Different profiles can be used by the same Snapshot
Monitor so that different calculations can be performed.
- phantom row
- A table row that can be read by
application processes that are executing with any isolation level except
repeatable read. When an application process issues the same query
multiple times within a single unit of work, additional rows can appear
between queries because of the data being inserted and committed by
application processes that are running concurrently.
- physical unit
- The component that manages and
monitors the resources (such as attached links and adjacent link stations)
associated with a node, as requested by an SSCP through an SSCP-PU
session. An SSCP activates a session with the PU in order to indirectly
manage, through PU, resources of the node such as attached links. This
term applies to types 2.0, 4, and 5 nodes only. See also control
point.
- point-in-time table
- A type of target table
whose content matches all or part of a source table, with an added system
column that identifies the approximate time when the particular row was
inserted or updated at the source system.
- point of consistency
- A point in time when all
the recoverable data a program accesses is consistent. The point of
consistency occurs when updates, inserts, and deletions are either committed
to the physical database or rolled back. Synonym for commit point and
sync point. See also rollback.
- precision
- In numeric data types, the total
number of binary or decimal digits excluding the sign.
- precompile
- To process programs containing
SQL statements before they are compiled. SQL statements are replaced
with statements that will be recognized by the host language compiler.
The output from a precompile includes source code that can be submitted to the
compiler and used in the bind process.
- predicate
- An element of a search condition
that expresses or implies a comparison operation.
- prefetch
- To read data ahead of, and in
anticipation of, its use.
- prepare
- To convert an SQL statement from
text form to an executable form, by submitting it to the SQL compiler.
- primary key
- A unique key that is part of the
definition of a table. A primary key is the default parent key of a
referential constraint definition.
- primary log
- A set of one or more log files
used to record changes to a database. Storage for these files is
allocated in advance. Contrast with secondary log.
- privilege
- The right to access a specific
database object in a specific way. These rights are controlled by users
with SYSADM (system administrator) authority or DBADM (database administrator)
authority or by creators of objects. Privileges include rights such as
creating, deleting, and selecting data from tables.
- procedure
- Synonym for stored
procedure.
- protocol.ini
- A file that contains LAN
configuration and binding information for all the protocol and medium access
control (MAC) system modules.
- PU
- Physical unit.
- public authority
- The authority for an object
granted to all users.
- PU type
- In SNA, the classification of a
physical unit (PU) according to the type of node on which it resides.
- Q
- quantified predicate
- A predicate that
compares a value with a set of values.
- query
- A request for information from the
database based on specific conditions; for example, a request for a list of
all customers in a customer table whose balance is greater than $1000.
- quiesce
- To end a process by allowing
operations to complete normally, while rejecting any new requests for
work.
- quoted name
- Synonym for delimited
identifier.
- R
- RDBMS
- Relational database management
system.
- read stability (RS)
- An isolation level that locks
only those rows that an application retrieves within a transaction. It
ensures that any qualifying row read during a transaction is not changed by
other application processes until the transaction is completed, and that any
row changed by another application process is not read until the change is
committed by that process. Read stability allows more concurrency than
repeatable read, and less than cursor stability.
- rebind
- To create a new package for an
application program that was previously bound. For example, if an index
is added for a table accessed by a program, the package must be rebound for it
to take advantage of the new index.
- record
- The storage representation of a
single row of a table.
- recording
- The information from performance
snapshots that can be viewed at a later time.
- recoverable log
- A database log in which all
log records are retained so that, in the event of a failure, lost data can be
recovered during forward recovery. Contrast with circular log.
- recovery
- (1) The act of resetting a system, or
data that is stored in a system, to an operable state following damage.
- (2) The process of rebuilding
databases by restoring a backup and rolling forward the logs associated with
it.
- recovery log
- See database log.
- recovery pending
- A state of the database or
table space. A database or table space is put in recovery pending state
when it is restored from a backup. While the database or table space is
in this state, its data cannot be accessed.
- recursion cycle
- The cycle that occurs when a
fullselect within a common table expression includes the name of the common
table expression in a FROM clause.
- recursive common table expression
- A common table
expression that refers to itself in a FROM clause from the fullselect.
Recursive common table expressions are used to write recursive queries.
- recursive query
- A fullselect that uses a
recursive common table expression.
- referential constraint
- The referential
integrity rule that the nonnull values of the foreign key are valid only if
they also appear as values of a parent key.
- referential integrity
- The state of a
database in which all values of all foreign keys are valid.
- refresh
- A process in which all of the data
of interest in a user table is copied to the target table, replacing existing
data.
- regular table space
- A table space that can
store any nontemporary data.
- rejected transaction
- A transaction
containing one or more updates from replica tables that are out of date in
comparison to the origin table.
- relational database
- A database that can be
perceived as a set of tables and manipulated in accordance with the relational
model of data.
- remote database
- A database that is physically
located on a workstation other than the one in use. Contrast with local
database.
- remote unit of work (RUOW)
- A unit of work that allows for the
remote preparation and execution of SQL statements.
- repeatable read (RR)
- An isolation level that locks all
the rows in an application that are referenced within a transaction.
When a program uses repeatable read protection, rows referenced by the program
cannot be changed by other programs until the program ends the current
transaction.
- replica
- A type of target table that can be
updated locally and receives updates from a user table through a subscription
definition. It can be a source for updating the user table or read-only
target tables.
- replication
- The process of taking changes
that are stored in the database log or journal at the source server and
applying them to the target server.
- replication administrator
- The user responsible for
defining replication sources and subscriptions. This user can also run
the Capture and Apply programs.
- replication source
- A database table that is
defined as a source for replication. This type of table can accept copy
requests and is the source table in a replication subscription set.
- replication subscription
- A specification for
copying changed data from replication sources to target tables at a specified
time and frequency, with the option of enhancing data. It defines all
of the information that is required by the Apply program to copy data.
- reserved word
- (1) In programming languages, a
keyword that may not be used as an identifier. (I)
- (2) A word used in a source
program to describe an action to be taken by the program or compiler.
It must not appear in the program as a user-defined name or a system
name.
- (3) A word that has been set aside
for special use in the SQL standard.
- restore
- To return a backup copy to the
active storage location for use.
- restore set
- A backup copy of a database or
table space plus zero or more log files that, when restored and rolled
forward, bring the database or table space back to a consistent state.
- result set
- Synonym for result table.
- result table
- The set of rows produced by the
evaluation of a SELECT statement. Synonymous with result set.
- revoke
- To remove a privilege or authority
from an authorization ID.
- RID (Record ID)
- A number that is used internally by
DB2 to uniquely identify a record in a table. It contains enough
information to address the page in which the record is stored.
- rollback
- The process of restoring data
changed by SQL statements to the state at its last commit point. See
also point of consistency.
- roll-forward
- The process of updating the
data in a restored database by applying changes recorded in the database
log. See forward recovery.
- row
- The horizontal component of a table
consisting of a sequence of values, one for each column of the table.
- RR
- Repeatable read.
- RS
- Read stability.
- RUOW
- Remote unit of work.
- S
- sargable
- A predicate that can be evaluated
as a search argument. See predicate.
- SBCS
- Single-byte character set.
- scalar fullselect
- A fullselect that returns
a single value-- one row of data consisting of exactly one column.
- scalar function
- An SQL operation that
produces a single value from another value and is expressed as a function name
followed by a list of arguments enclosed in parentheses.
- scale
- The number of digits in the
fractional part of a number.
- schema
- A collection of database objects
such as tables, views, indexes, or triggers. It provides a logical
classification of database objects.
- SDK
- Software Developer's Kit.
- search condition
- A criterion for selecting
rows from a table. A search condition consists of one or more
predicates.
- secondary log
- A set of one or more log files
used to record changes to a database. Storage for these files is
allocated as needed when the primary log is full.
- self-referencing row
- A row that is a parent
of itself.
- self-referencing subquery
- A subselect or
fullselect within a DELETE, INSERT, or UPDATE statement that refers to the
same table that is the object of the SQL statement.
- self-referencing table
- A table that is both a
parent and a dependent table in the same referential constraint.
- server
- In a network, a node that provides
facilities to other stations; for example, a file server, a printer server, a
mail server.
- service name
- A name that provides a symbolic
method of specifying the port number to be used at a remote node. The
TCP/IP connection requires:
- The address of the remote node.
- The port number to be used on the remote node to identify an
application.
- session
- A logical connection between two
stations or SNA network addressable units (NAUs) that allows the two stations
or NAUs to communicate.
- session limit
- In SNA, the maximum number of
concurrently active logical unit-logical unit (LU-LU) sessions that a
particular logical unit (LU) can support.
- session partner
- In SNA, one of the two
network addressable units (NAUs) participating in an active session.
- session security
- For LU 6.2, partner
LU verification and session data encryption. A Systems Network
Architecture (SNA) function that allows data to be transmitted in encrypted
form.
- set operator
- The SQL operators UNION,
EXCEPT, and INTERSECT corresponding to the relational operators union,
difference, and intersection. A set operator derives a result table by
combining two other result tables.
- shadowing
- A recovery technique in which
current page contents are never overwritten. Instead, new pages are
allocated and written while the pages whose values are being replaced are
retained as shadow copies until they are no longer needed to support the
restoration of the system state due to a transaction rollback.
- share lock
- A lock that limits concurrently
executing application processes to read-only operations on database
data.
- short string
- A fixed-length string or a
varying-length string whose maximum length is less than or equal to 254
bytes.
- single-byte character set (SBCS)
- A character set in which each
character is represented by a one-byte code. Contrast with double-byte
character set, multi-byte character set.
- SMS table space
- System managed space table
space.
- SNA
- Systems Network Architecture.
- SNA network
- The part of the user application
network that conforms to the formats and protocols of Systems Network
Architecture (SNA). It enables reliable transfer of data among users
and provides protocols for controlling the resources of various network
configurations. The SNA network consists of network addressable units
(NAUs), gateway function, intermediate session routing function components,
and the transport network.
- snapshot
- See performance snapshot, explain
snapshot.
- Snapshot Monitor
- An API used to assess the
status of the database manager, individual databases, tables, table spaces,
and individual applications.
- soft checkpoint
- The process of writing some
information to the log file header; this information is used to determine the
starting point in the log in case a database restart is required.
- Software Developer's Kit (SDK)
- An application development product that
allows applications to be developed on a client workstation to access remote
database servers including host relational databases through the DB2 Connect
products.
- source function
- A user-defined function
(UDF) whose body is used to implement one or more other UDFs.
- source server
- The database location of the
replication source and the Capture program.
- source table
- A table that contains the data
that is to be copied to a target table. The source table can be a
replication source table, a change data table, or a consistent change data
table. Contrast with target table.
- source type
- An existing type that is used to
internally represent a distinct type.
- special register
- A storage area that is
defined for an application process by the database manager and is used to
store information that can be referenced in SQL statements. Examples
are USER and CURRENT DATE.
- specific function name
- The name that uniquely
identifies a function to the system.
- SQL
- A standardized language for defining
and manipulating data in a relational database.
- SQLCA
- SQL communication area.
- SQL communication area (SQLCA)
- A set of variables that provides
an application program with information about the execution of its SQL
statements or its requests from the database manager.
- SQLDA
- SQL descriptor area.
- SQL descriptor area (SQLDA)
- A set of variables that is used
in the processing of certain SQL statements. The SQLDA is intended for
dynamic SQL programs.
- SSCP
- System services control point.
- stack
- An area in memory that stores
temporary register information, parameters, and return addresses of
subroutines.
- staging table
- A consistent change target
table that is used as the source for updating data to multiple target
tables.
- standard conflict detection
- Conflict
detection in which the Apply program searches for conflicts in rows that are
already captured in the replica's change data tables. See also
conflict detection, enhanced conflict detection.
- statement
- An instruction in a program or
procedure.
- statement handle
- In CLI, a handle that
refers to the data object that contains information about an SQL
statement. This includes information such as dynamic arguments,
bindings for dynamic arguments and columns, cursor information, result values,
and status information. Each statement handle is associated with a
connection handle.
- static SQL
- SQL statements that are embedded
within a program, and are prepared during the program preparation process
before the program is executed. After being prepared, a static SQL
statement does not change, although values of host variables specified by the
statement may change.
- stored procedure
- A block of procedural
constructs and embedded SQL statements that is stored in a database and can be
called by name. Stored procedures allow an application program to be
run in two parts. One part runs on the client and the other on the
server. This allows one call to produce several accesses to the
database. Synonymous with procedure.
- string
- In programming languages, the form
of data used for storing and manipulating text.
- Structured Query Language
- See SQL.
- subagent
- A type of agent that works on
subrequests. A single application can make many requests, and each
request can be broken into many subrequests. Therefore, there can be
multiple subagents working on behalf of the same application. All
subagents working for the application are coordinated by the coordinating
agent for that application. See also coordinating agent.
- subordinate agent
- See subagent.
- subquery
- A fullselect used within a search
condition of an SQL statement.
- subscription cycle
- The processing of a
subscription set by the Apply program.
- subscription set
- The specification of a
group of source tables, target tables, and the control information that
governs the replication of changed data. Updates are committed in the
same transaction.
- subselect
- That form of a query that does
not include an ORDER BY clause, an UPDATE clause, or UNION operators.
- symbolic destination name
- Specifies the name
of a remote partner. The name corresponds to an entry in the CPI
Communications side information table that contains the necessary information
(partner LU name, mode name, partner TP name) for the client to set up an APPC
connection to the server.
- synchronization level
- In APPC, the specification
indicating whether the corresponding transaction programs exchange
confirmation requests and replies.
- synchronous
- Pertaining to two or more processes
that depend upon the occurrences of specific events, such as a common timing
signal. Contrast with asynchronous.
- sync point
- Synonym for point of
consistency.
- system catalog
- See catalog.
- system database directory
- A directory that contains
entries for every database that can be accessed using the database
manager. It is created when the first database is created or cataloged
on the system.
- system managed space (SMS) table space
- A table space whose space is
managed by the operating system. This storage model is based on files
created under subdirectories, and managed by the file system. Contrast
with database managed space (DMS) table space.
- system services control point (SSCP)
- The control point in a SNA network
that provides network services for dependent nodes.
- Systems Network Architecture (SNA)
- The description of the logical
structure, formats, protocols, and operational sequences for transmitting
information units through the networks and also the operational sequences for
controlling the configuration and operation of networks.
- T
- table
- A named data object consisting of a
specific number of columns and some unordered rows.
- table designator
- A column name qualifier
that designates a specific object table.
- table queue
- A mechanism for transferring
rows between database nodes. Table queues are distributed row streams
with simplified rules for the insertion and removal of rows. Table
queues can also be used to deliver rows between different processes in the
serial database.
- table space
- An abstraction of a collection
of containers into which database objects are stored. A table space
provides a level of indirection between a database and the tables stored
within the database. A table space:
- Has space on media storage devices assigned to it.
- Has tables created within it. These tables will consume space in
the containers that belong to the table space. The data, index, long
field, and LOB portions of a table can be stored in the same table space, or
can be individually broken out into separate table spaces.
See also system managed space (SMS) table space, database managed space
(DMS) table space, long table space, regular table space, temporary table
space.
- table space container
- A generic term
describing an allocation of space to a table space. Depending on the
table space type, the container can be a directory, device, or file.
- target server
- The database location of the
target table. Normally this is also the location of the Apply
program.
- target table
- The table on the target server
to which data is copied. It can be a user copy table, a point-in-time
table, a base aggregate table, a change aggregate table, a consistent change
data table, or a replica table.
- TCP/IP
- Transmission Control
Protocol/Internet Protocol.
- temporary table
- A table created during the
processing of an SQL statement to hold intermediate results.
- temporary table space
- A table space that can store
only temporary tables.
- territory
- A portion of the POSIX** locale
that is mapped to the country code for internal processing by the database
manager.
- thread
- In some operating systems, the
smallest unit of operation to be performed in a process.
- threshold trigger
- An event occurring when
the value of a performance variable exceeds or falls below a user-defined
threshold value. The action that occurs as a result of a threshold
trigger could be:
- Logging information in an alert log file
- Displaying information in an alert log window
- Generating an audio alarm
- Issuing a message window
- Invoking a predefined command or program
- time
- A three-part value that designates a
time of day in hours, minutes, and seconds.
- time duration
- A DECIMAL(6,0) value that
represents a number of hours, minutes, and seconds.
- timeron
- A unit of measurement used to give
a rough relative estimate of the resources, or cost, required by the database
server to execute two plans for the same query. The resources
calculated in the estimate include weighted CPU and I/O costs.
- timestamp
- A seven-part value that consists
of a date and time expressed in years, months, days, hours, minutes, seconds,
and microseconds.
- timestamp duration
- A DECIMAL(20,6) value
that represents a number of years, months, days, hours, minutes, seconds, and
microseconds.
- TM Database
- Transaction Manager Database.
- TP
- Transaction program.
- token
- The basic syntactic unit of a
computing language. A token consists of one or more characters,
excluding the blank character, and excluding characters within a string
constant or delimited identifier.
- topology and routing services (TRS)
- An APPN control point component
that manages the topology database and computes routes.
- trace table
- A table that contains a
high-level record of the execution of the Capture program.
- transaction
- An exchange between a
workstation and a program, two workstations, or two programs that accomplish a
particular action or result. An example is the entry of a
customer's deposit and the update of the customer's balance.
Synonym for unit of work.
- transaction compensation
- A process that
restores rows that are affected by a committed transaction that is
rejected. When a committed transaction is rejected, the rows are
restored to the state that they were in before the transaction was
committed.
- transaction manager
- Assigns identifiers to
transactions, monitors their progress, and takes responsibility for
transaction completion and failure recovery.
- Transaction Manager Database (TM Database)
- A database that is used to log
transactions when a two-phase commit (SYNCPOINT TWOPHASE) is used with DB2
databases. In the event of transaction failure, the TM Database
information can be accessed to resynchronize databases involved in the failed
transaction.
- transaction program (TP)
- An application program that uses
APPC to communicate with a partner application program.
- transition table
- A named temporary table
that contains the transition values for each row affected by the triggering
modification. An old transition table contains the values of affected
rows before the modification is applied, and a new transition table contains
the values of the affected rows after the modification is applied.
- transition variable
- A variable that is valid
only in FOR EACH ROW triggers. It allows access to the transition
values for the current row. An old transition variable is the value of
the row before the modification is applied, and the new transition variable is
the value of the row after the modification is applied.
- Transmission Control Protocol/Internet Protocol (TCP/IP)
- A set of communications protocols
that provide peer-to-peer connectivity functions for both local and wide area
networks.
- trigger
- In DB2, an object in a database
that is invoked indirectly by the database manager when a particular SQL
statement is run.
- triggered action
- The action that is executed
when the trigger event occurs.
- triggered-action condition
- The search
condition that controls the execution of the SQL statements within the
triggered action.
- trigger event
- In a trigger definition, an
update operation (INSERT, UPDATE, or DELETE statement) that causes the trigger
to be run.
- truncation
- The process of discarding part
of a result from an operation when it exceeds memory or storage
capacity.
- tuning parameters table
- A table at the source
server that contains timing information used by the Capture program.
The information includes:
- How long to keep rows in the change data table.
- How much time can elapse before changes are stored in a database log or
journal.
- How often to commit changed data to the unit of work tables.
- two-phase commit
- A two-step process by which
recoverable resources and an external subsystem are committed. During
the first step, the database manager subsystems are polled to ensure that they
are ready to commit. If all subsystems respond positively, the database
manager instructs them to commit.
- typed parameter marker
- A parameter marker
that is specified along with its target data type. It has the general
form:
CAST(? AS data-type)
- U
- UDF
- User-defined function.
- UDT
- User-defined type.
- unambiguous cursor
- A cursor that has been
defined in a manner that allows a relational database to determine whether
blocking can be used with the answer set. A cursor defined FOR FETCH
ONLY or FOR READ ONLY can be used with blocking, whereas a cursor defined FOR
UPDATE cannot.
- unbind session (UNBIND)
- A request to deactivate a
session between two logical units (LUs).
- uncommitted read (UR)
- An isolation level that allows an
application to access uncommitted changes of other transactions. The
application does not lock other applications out of the row it is reading,
unless the other application attempts to drop or alter the table.
- uncoordinated transaction
- A transaction that
accesses more than one resource but its commit or rollback is not being
coordinated by a Transaction Manager.
- Unicode**
- An international character encoding
scheme that is a subset of the ISO 10646 standard. Each character
supported is defined using a unique 2-byte code.
- unique constraint
- The rule that no two
values in a primary key or key of a unique index can be the same.
- unique index
- An index that ensures that no
identical key values are stored in a table.
- unique key
- A key that is constrained so that
no two of its values are equal.
- unit of work
- A recoverable sequence of
operations within an application process. At any time, an application
process is a single unit of work, but the life of an application process can
involve many units of work as a result of commit or rollback
operations. Synonym for transaction.
- unit-of-work table
- A replication control table
at the source server that contains commit records read from the database log
or journal. The records include a unit-of-recovery ID that can be used
to join the unit-of-work table and the change data table to produce
transaction-consistent change data. For DB2, the unit-of-work table
optionally includes the correlation ID, which can be useful for auditing
purposes.
- untyped parameter marker
- A parameter marker
that is specified without its target data type. It has the form of a
single question mark.
- update rule
- A condition enforced by the
database manager that must be met before a column can be updated.
- UR
- Uncommitted read.
- user copy table
- A target table whose content
matches all or part of a source table and contains only user data
columns.
- user-defined distinct type
- See distinct
type.
- user-defined function (UDF)
- A function that is defined to the
database management system and can be referenced thereafter in SQL
queries. It can be one of the following functions:
- An external function, in which the body of the function is written in a
programming language whose arguments are scalar values and a scalar result is
produced for each invocation.
- A sourced function, implemented by another built-in or user-defined
function already known to the DBMS. This function can be either a
scalar function or column (aggregating) function, and returns a single value
from a set of values (for example, MAX or AVG).
- user-defined performance variable
- A performance variable
created by a user and added to the performance variable profile.
- user-defined target table
- Any type of target
table that is created by a user for an application and can be used in the
replication process.
- user-defined type (UDT)
- A data type that is not native to
the database manager and was created by a user. See also distinct type.
- user table
- A table created for and used by
an application before it is defined as a replication source. It is used
as the source for updates to read-only target tables, consistent change data
tables, and replicas.
- UTC
- Coordinated Universal Time.
- V
- value
- (1) Smallest unit of data manipulated in
SQL.
- (2) A specific data item at the
intersection of a column and a row.
- variable
- A data element that specifies a
value that can be changed.
- variant function
- A user-defined function
whose result is dependent on its input parameter values as well as other
factors. Successive invocations with the same parameter values might
produce different results. Contrast with not-variant function.
- varying-length string
- A character, graphic,
or binary string whose length is not fixed but can range within set
limits.
- view
- A logical table that consists of data
that is generated by a query.
- Visual Explain
- A tool that lets database
administrators and application programmers use a graphical interface to
display and analyze detailed information on the access plan of a given SQL
statement. The tasks provided by this tool can be accessed from the
Control Center.
- W
- warm start
- A restart that allows reuse of
previously initialized input and output work queues. Contrast with cold
start.
- warm start table
- A table used by the Capture
program to save position in a DBMS log for later reference during warm
start.
- well known address
- An address used to
uniquely identify a particular node in the network to establish connections
between nodes. The well known address is a combination of the network
address and the port used on the logical node.
- X
- XID
- Exchange station ID.
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