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Status Delivered
Workspace Db2 for z/OS
Created by Guest
Created on Jul 19, 2019

RELATED IDEAS

Change IRLM hashing algorithm to offer a better and more efficient distribution of P-locks across LTEs

See this idea on ideas.ibm.com

As per PMR 76883,999,866/TS002531202, when increasing DSMAX and PCLOSET/N parms to reduce TCB DBM1 CPU time owing to less open/close operations, we noticed a significant increase in IRLM CPU time, strongly correlated with higher number of currently opened datasets.  Further PMR analysis has  shown that IRLM hashing algorithm can hash so many pageset/partition P-locks into a relatively small set of LTEs, that it makes IRLM deadlock detection processing very expensive. This is because IRLM deadlock processing is having problems with very long chains of resources per hash value, which in turn causes significant CPU overhead. This is especially visible when IRLM needs to hash a large number of partitions defined on the same DBID. That is a serious scaling limitation which cannot be easily resolved. This issue has been discussed with IBM in more detail and it has been suggested that IRLM hashing algorithm may have to be redesigned.

  • Admin
    Janet Figone
    Reply
    |     Dec 11, 2019

    We are pleased to inform you this AHA Idea has been delivered via APAR PH17336/PTF UI66284. We appreciate your input and hope you will continue to submit your Ideas for our consideration for the Db2 for z/OS product.

  • Guest
    Reply
    |     Dec 11, 2019

    This idea is implemented by PH17336/UI66284.  UI66284 is available for order.

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