DB2 10.5 for Linux, UNIX, and Windows

Specifying a lock wait mode strategy

A session can specify a lock wait mode strategy, which is used when the session requires a lock that it cannot obtain immediately.

The strategy indicates whether the session will:

Return an SQLCODE and SQLSTATE when it cannot obtain a lock
Wait indefinitely for a lock
Wait a specified amount of time for a lock
Use the value of the locktimeout database configuration parameter when waiting for a lock

The lock wait mode strategy is specified through the SET CURRENT LOCK TIMEOUT statement, which changes the value of the CURRENT LOCK TIMEOUT special register. This special register specifies the number of seconds to wait for a lock before returning an error indicating that a lock cannot be obtained.

Traditional locking approaches can result in applications blocking each other. This happens when one application must wait for another application to release its lock. Strategies to deal with the impact of such blocking usually provide a mechanism to specify the maximum acceptable duration of the block. That is the amount of time that an application will wait prior to returning without a lock. Previously, this was only possible at the database level by changing the value of the locktimeout database configuration parameter.

The value of locktimeout applies to all locks, but the lock types that are impacted by the lock wait mode strategy include row, table, index key, and multidimensional clustering (MDC) block locks.