Number of Lock Escalations

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, or the lock list space consumed by all applications is approaching the total lock list space. The amount of lock list space available is determined by the maxlocks and locklist 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"), or those that are holding too much of the lock list, using the following formula:

    (((locks held * 36) / (locklist * 4096)) * 100)
  

  and comparing the value to maxlocks. These applications 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.