Ultimate lock holder

The ultimate holder of a program isolation lock is one of the following holders:

  • A region holding the lock required by another region
  • A region holding the lock required by a waiting region that is holding a different lock required by another waiting region

Related topic

Analyze-program-isolation-lock-contention

Example

Region 1 is running and holds lock A

Region 2 is waiting for lock A

Region 1 is the ultimate holder of the lock required by Region 2.

Example

Region 1 is running and holds lock A

Region 2 is waiting for lock A and holds lock B

Region 3 is waiting for lock B

Region 1 is the ultimate holder of the lock that must be freed before Region 2 and Region 3 can continue processing.

The ultimate holder of a lock is significant because the ultimate holder must release the lock before other work can proceed. The ultimate holder can release the lock either by:

  • Completing normally
  • Completing expeditiously (influenced by operations control or by an increase in the region’s performance level)
  • Being stopped with a P or PA region stop line command (see Line-commands-Program-isolation-lock-views)

Before you use a stop command on an ultimate region to free a lock, you should consider the amount of time that backout processing will take as a result of the stop command. If the region is an errant BMP, stopping the region may take longer than allowing processing to complete.

In example 2, neither Region 3 nor Region 2 will continue processing until Region 1 releases lock A, and you cannot cause Region 2 to release its lock without terminating the IMS control region. Region 1 is the cause of the problem, and the only way to solve the problem is to influence the processing of Region 1, the ultimate lock holder.

Important

There may be more than one ultimate holder of a lock when regions hold shared locks and the requester requires an exclusive lock.

 

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