Changing the lock structure size dynamically

If certain conditions are met, you can dynamically change the size of a lock structure.

About this task

You can dynamically change the lock structure size if all the following conditions are true:

  • The lock structure is allocated in a coupling facility with CFLEVEL greater than zero.
  • The currently allocated size of the structure is less than the maximum size that is defined in the SIZE parameter of the CFRM policy.

Procedure

To dynamically change the lock structure size:

Issue the SETXCF START,ALTER command.

Example

For example, use the following command to change the lock structure size for group DSNDB0A:
SETXCF START,ALTER,STRNAME=DSNDB0A_LOCK1,SIZE=newsize

This example assumes that newsize is less than or equal to the maximum size that is defined in the CFRM policy for the lock structure. If the maximum size (SIZE in the CFRM policy) is still not big enough, you must increase the lock storage in the CFRM policy and rebuild the lock structure.

Important: For a duplexed lock structure, you are changing the size of both the primary and secondary structure with a single command.

Because the dynamic method affects only the record table entries portion of the lock structure, the impact of changing the lock size can have a disproportionately large effect on the record table list portion of the structure. For example, if you halve the size of the lock structure, it can result in all of the available record table entries being taken away—probably not the result you want. For the same reason, if you double the lock structure size, the increased storage space is used entirely by the record table unless a rebuild occurs or the group is shut down, the structure is forced, and the group is restarted. If either of these are done after the size is changed, the split of the new structure is determined by the number of lock table entries requested by the first IRLM to connect to the group.