Lock Escalations

Snapshot Information Level
Database
Application

API Structure(s)
sqlm_dbase
sqlm_appl

Monitor Group
Basic
Basic

Resettable

Yes

Event Information Level
Database
Connection
Transaction

API Structure(s)
sqlm_db_event
sqlm_conn_event
sqlm_xaction_event

API Element Name
Element Type

lock_escals
counter

Description:  The number of times that locks have been escalated from several row locks to a table lock.

Usage:  A lock is escalated when the total number of locks held by an application reaches the maximum amount of lock list space available to the application. The amount of lock list space available is determined by the locklist and maxlocks configuration parameters.

When an application reaches the maximum number of locks allowed and there are no more locks to escalate, it will then use space in the lock list allocated for other applications. When the entire lock list is full, an error occurs.

This data item includes a count of all lock escalations, including exclusive lock escalations.

There are several possible causes for excessive lock escalations:

• The lock list size (locklist) may be too small for the number of concurrent applications
• The percent of the lock list usable by each application (maxlocks) may be too small
• One or more applications may be using an excessive number of locks.

To resolve these problems, you may be able to:

• Increase the locklist configuration parameter value. See the Administration Guide for a description of this configuration parameter.
• Increase the maxlocks configuration parameter value. See the Administration Guide for a description of this configuration parameter.
• Identify the applications with large numbers of locks. (See "Maximum Number of Locks Held".) They can also cause lock escalations in other applications by using too large a portion of the lock list. These applications may need to resort to using table locks instead of row locks, although table locks may cause an increase in Lock Waits and Time Waited On Locks.
• Identify applications holding too much of the lock list, using the following formula:

    (((locks held * 32) / (locklist * 4096)) * 100)
  

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