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Stop package invalidation after ALTER MAXPARTITIONS

These days in an agile world we have to ALTER PBG spaces on-the-fly to raise the MAXPARTITIONS value. Sadly this ALTER, even though it is an immediate ALTER, sets all dependent packages to VALID = 'N' which is, of course, a disaster.

  • Avatar32.5fb70cce7410889e661286fd7f1897de Guest
  • Oct 30 2019
  • Future Consideration
Why is it useful?
Who would benefit from this IDEA? Everyone who uses PBGs on z/OS.
How should it work?

The ALTER of MAXPARTITIONS should not invalidate any packages. I cannot even think what this ALTER  could possibly have to do with the access plan (path). The "new" PBR RPN *can* be ALTERed with a higher DSSIZE for TP and IP so I see no reason why PBGs cannot also be ALTERed like this.

Idea Priority Urgent
Priority Justification Auto rebind in production is *never* a desired outcome....
Customer Name Software Engineering GmbH
Submitting Organization
Submitter Tags
  • Attach files
  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    26 May 09:48pm

    Hello,

    So yes, parallelism can put key ranges into the access path, and so can limited partition scan. Reorg rebalance, insert partition, alter table rotate part,

    Best regards,

    Pat Bossman

  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    7 May 11:05am

    A similar issue occurs with the Reorg Rebalance, why does it set VALID='N' for all related packages?

    Sergi.

  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    29 Nov, 2019 10:07am

    ahh now I understand why MAXPARTITIONS can have an impact. But at what level? If I define a MAXPARTITIONS at say 256 is it seriously going to assume I can run with 256 parallel sub-tasks?? Surely not! I could believe this with up to 16 but above that I cannot really think it is ever used...

  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    12 Nov, 2019 01:59pm

    Per IBM the reason that the packages are invalidated due to parallelism.  But I'd like to recommend that if the packages are bound with Degree(1), that they are not invalidated.  

    When parallelism build a parallel group partitioned on page range, it will use the current defined MAXPARTITIONS as the high bound (the maximum partition or pages can the table have). So, when MAXPARTITIONS increase, then any newly added partitions will be out-of-the-parallel-group-scan-boundary. Hence, causes incorrect output (whatever the data resides in the newly added partitions, will never have a change to be examined). In order to correct the behavior, we request the previous bound parallel plan to be rebound(invalidate the package for a rebind) to make sure we cover the newly defined/added partitions.

    On the other hand, if the MAXPARTITIONS is decreased, then the parallel group will still cover the whole range and Date Manager guarantee that if the needs to be scanned page/partition is over the maximum physical page/partition, it will simply returns EOF. So, no re-bind needed in this path.

    Hope this answer your question. Please let us know If you have any further question or concern.

  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    30 Oct, 2019 02:35pm

    With only impact to catalog, not sure how Access Path would be impacted.  Seems wasteful and counter productive to invalidate packages.

  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    30 Oct, 2019 01:49pm

    I opened a Case on this asking why packages are being invalidated in this situation and it is still open waiting for a reply.

  • Avatar40.8f183f721a2c86cd98fddbbe6dc46ec9
    Guest commented
    30 Oct, 2019 01:41pm

    this is just a limit in the catalog.  So how could access path be affected ?  The actual growth of a partition doesn't invalidate the package so how just changing the limit do so ?

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