Delaying deadlock checking

Adaptive Server performs deadlock checking after a minimum period of time for any process waiting for a lock to be released (sleeping). This deadlock checking is time-consuming overhead for applications that wait without a deadlock.

If your applications deadlock infrequently, Adaptive Server can delay deadlock checking and reduce the overhead cost. You can specify the minimum amount of time (in milliseconds) that a process waits before it initiates a deadlock check using the configuration parameter deadlock checking period.

Valid values are 0–2147483. The default value is 500. deadlock checking period is a dynamic configuration value, so any change to it takes immediate effect.

If you set the value to 0, Adaptive Server initiates deadlock checking when the process begins to wait for a lock. If you set the value to 600, Adaptive Server initiates a deadlock check for the waiting process after at least 600 ms. For example:

sp_configure "deadlock checking period", 600

Setting deadlock checking period to a higher value produces longer delays before deadlocks are detected. However, since Adaptive Server grants most lock requests before this time elapses, the deadlock checking overhead is avoided for those lock requests.

Adaptive Server performs deadlock checking for all processes at fixed intervals, determined by deadlock checking period. If Adaptive Server performs a deadlock check while a process’s deadlock checking is delayed, the process waits until the next interval.

Therefore, a process may wait from the number of milliseconds set by deadlock checking period to almost twice that value before deadlock checking is performed. sp_sysmon can help you tune deadlock checking behavior.

See “Deadlock detection”.