Handling high-volume publish/subscribe activity on z/OS

Brokers that handle large numbers of retained subscriptions or publications can use up all the IRLM storage that is allocated by default for DB2® locks. Using up all the IRLM storage might cause problems when you try to restart the broker.

The following actions might prevent you from using up all the IRLM storage and thereby avoid problems when you try to restart the broker:

  1. Tune the publish/subscribe topology:
    1. Balance execution groups across more brokers; by balancing execution groups across more brokers, you cause fewer execution groups to require to start at the same time and to have concurrent locks for the same DB2 subsystem.
    2. Put the brokers in publish/subscribe collectives; by putting the brokers in collectives, you reduce the number of subscriptions in a single broker table, and also reduce the amount of concurrent access to DB2. See Publish/subscribe topologies for more information.
  2. Increase the IRLM storage that is available:
    1. Set the value of MAXCSA so high that the ECSA that is required by the IRLM never reaches this value. Because IRLM gets storage only when it needs it, choose a value that is higher than you expect IRLM to require.
    2. If you are unable to choose a value of MAXCSA that is sufficiently high that it cannot be exceeded by the ECSA that is required by the IRLM, use the option PC=YES on the START irlmproc command. By using this option, you cause the IRLM to place in its private address space the control block structures that relate to locking. See the DB2 V7 library (z/OS®) or DB2 information center (z/OS) (Version 8) for more information.
Note: There might be a slight (approximately 1 to 2 percent) performance degradation when you use the PC=YES option on the START irlmproc command.
Related tasks
Resolving problems when using publish/subscribe
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Copyright IBM Corporation 1999, 2009Copyright IBM Corporation 1999, 2009.
Last updated : 2009-01-07 15:22:59

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