Db2 for z/OS & Db2ZAI

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  • 1.  Use of Relative Page Numbering (RPN)

    InnerCircle
    Posted Tue April 12, 2022 01:15 PM
    Edited by Portia Melita Wed April 13, 2022 09:13 AM
    Hello everyone.
    Like so many others, we also operate tables that are growing tremendously.
    In this context, we are considering applying 'Pagenum relative' to the large PBRs.
    I want to hear if others have experience, good or bad, with the feature that apparently resembles any DBA's dream.
    Thanks in advance.

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    Morten Liedecke
    Technical Lead Db2 for z/OS DBA
    JN Data
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  • 2.  RE: Use of Relative Page Numbering (RPN)

    IBM Champion
    Posted Thu August 11, 2022 02:11 AM
    Hi!
     Best feature in Db2 12 if you ask me... If you monitor extents (IFCID 258) you can even ALTER the DSSIZE on the fly while a LOAD is running and it works great! Same is true for index sizing. Naturally you still have to take care of the 1024GB partition limit as then you must repartition obviously. All in all a no brainer!

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    Roy Boxwell
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  • 3.  RE: Use of Relative Page Numbering (RPN)

    InnerCircle
    Posted Fri August 12, 2022 01:53 AM
    Hi,
    Thanks for your reply.
    We now use RPM and it works great. 
    The only but necessary challenge we have experienced is getting through the initial reorg on very large tablespaces.
    But otherwise I can only encourage everyone to get started.

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    Morten Liedecke
    Technical Lead Db2 for z/OS DBA
    JN Data
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  • 4.  RE: Use of Relative Page Numbering (RPN)

    Posted Fri August 12, 2022 08:19 PM

    Hi,
    Do you think it is a good idea to set Db2 z/OS v12 zparm PAGESET_PAGENUM as RELATIVE ?

    Thanks, Pol.



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    Jose Eduardo Pol
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  • 5.  RE: Use of Relative Page Numbering (RPN)

    Posted Fri August 12, 2022 08:19 PM

    Hi,
    Do you think it is a good idea to set Db2 z/OS v12 zparm PAGESET_PAGENUM as RELATIVE ?

    Thanks, Pol.



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    Jose Eduardo Pol
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  • 6.  RE: Use of Relative Page Numbering (RPN)

    IBM Champion
    Posted Mon August 15, 2022 02:56 AM
    Hi!
     Yes indeed - it is changed to be default in Db2 13 anyway and I see no reason not to use it as a default now.

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    Roy Boxwell
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  • 7.  RE: Use of Relative Page Numbering (RPN)

    Posted Tue August 16, 2022 02:08 PM
    Some additional clarification, please?  As I understand things:
    • RPN applies only to PBR tablespaces.
    • There are no performance implications of RPN, good/bad/indifferent, during the normal course of affairs.
    • RPM mandates IC by partition, if inline to a REORG.

    Yes?

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    Mike Brauweiler
    Consulting Systems Engineer
    Mainline Information Systems
    6302094905
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  • 8.  RE: Use of Relative Page Numbering (RPN)

    IBM Champion
    Posted Wed August 17, 2022 01:27 AM
    Hi!
     Yep, PBR RPN is an extension to PBR. PBR RPN should be no different in performance from a regular PBR. To migrate from PBR to PBR RPN you must do inline TP level copies. Once you are at PBR RPN you are again free to copy at the TS/TP level.

    Hope that helps!

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    Roy Boxwell
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  • 9.  RE: Use of Relative Page Numbering (RPN)

    Posted Tue August 16, 2022 03:15 AM
    Hi Pol
    relative page numbering (RPN) is best practice for PBR table spaces.

    –RPN advantages versus absolute page numbering:

    • Much greater data capacity
    • Maximum number of partitions not affected by choice of page size or DSSIZE
    • DSSIZE can be specified at partition level (and DSSIZE increase is immediate change)

    –Also: when PBG table space is online-converted to PBR via Db2 13 enhancement, RPN is used for the new PBR table space

    –And conversion from absolute to relative page numbering requires online REORG of entire table space, and that gets more expensive as table space gets larger, therefore best to start out with RPN for a PBR table space as default.

    Regards, Cuneyt Goksu



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    MEHMET CUNEYT GOKSU
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  • 10.  RE: Use of Relative Page Numbering (RPN)

    Posted Wed August 17, 2022 07:36 AM
    The Db2 13 "What's New" documentation (Overview of what's new in Db2 13 - IBM Documentation) hints that Absolute Page Numbering will be deprecated, although this word is not used.  Here's the paragraph from the online documentation that discusses the default for the PAGESET_PAGENUM zParm.  I highlighted two key statements that everyone needs to be aware of.

    Relative page numbering for new PBR table spaces

    Starting in function level 100, the default value of the PAGESET_PAGENUM subsystem parameter is changed to RELATIVE. The PAGESET_PAGENUM subsystem parameter specifies the default value that Db2 uses when you omit the PAGENUM option in CREATE TABLESPACE or CREATE TABLE statement for a partition-by-range (PBR) table space. That is, it specifies whether Db2 creates the table space and associated partitioned indexes to use relative page numbers (RPN) or absolute page numbers (APN) across partitions. RPN is the strategic direction for PBR table spaces in Db2. If you accept the new default and create all new PBR table spaces with relative page numbers, you can avoid costly future conversions. Converting from absolute to relative pages numbers always requires a REORG of the entire table space.

    As for the REORG that does the conversion, the REORG must be table space level and partition level image copies are required.  The new ICLIMIT_DASD or ICLIMIT_TAPE option in the REORG (Db2 12 and 13) will limit the number of devices that are allocated to the job for the image copy data sets. 

    Be aware that when the RPN conversion is applied, the partitioned index will be implicitly altered by Db2 to set the index's DSSIZE value to its current value, which corresponds to the table space's DSSIZE.  Once the table space is converted to PBR RPN, the table space and index DSSIZE are independent.  The index DSSIZE cannot be altered prior to the PBR RPN conversion, however it can be altered after the conversion.  According to the Db2 documentation, the index DSSIZE cannot be altered to a smaller value, only a larger value.  The index DSSIZE alter is immediate.

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    STEPHEN NEWTON
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