DB2 Replication Guide and Reference

DB2 for MVS Rules Regarding Indexes

Do not specify TYPE 1 indexes if the table space containing the identified table has a LOCKSIZE or ROW. If you specify TYPE 1 in a data sharing environment, a warning message is issued if you specify a value greater than 1 for SUBPAGES. A TYPE 1 index with more than one subpage cannot be accessed when there is inter-DB2 read/write interest in the index.

You cannot use an isolation UR option with an access path that uses a TYPE 1 index.

TYPE 2 indexes are a new type of index in MVS Version 4. Because TYPE 2 indexes do not lock index pages, your applications can avoid deadlock and timeout problems on the index. The key advantage of TYPE 2 indexes is that they allow you to use other Version 4 enhancements, such as parallel query central processor (CP) processing, improved partition independence, row locking, and the ability to read through locks. If you specify TYPE 2, all specifications of SUBPAGES are ignored, and an error message is issued.

If you do not specify a type of index, the type is determined as follows:

If the LOCKSIZE is ROW, the default index type is TYPE 2 regardless of the type specified on the installation panel DSNTIPE.
If the LOCKSIZE is not ROW, the default index type is the type specified in the field DEFAULT INDEX TYPE on the installation panel DSNTIPE. The default value for that field is TYPE 2.

Recommendation

Defer all MVS 4.1 table indexes as TYPE 2. For best IBM Replication performance, you should bind the Capture and Apply programs using isolation UR. When using this option, all indexes on the control tables are required to be created as TYPE 2 indexes. In addition, if source views are being used in replication subscriptions, and the Apply program is bound using isolation UR, then only TYPE 2 indexes over the registered source tables involved in the source view are usable by the Apply program.
For a DB2 for MVS or DB2 for OS/390 source servers specify the TYPE 2 clause on every generated CREATE INDEX statement and every create index statement in the DB2 UDB Control Center file DPCNTL.MVS.

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