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  • 1.  pgsteal none - VPSEQT=100 or VPSEQT=0????

    Posted Mar 29, 2022 01:14 PM

    Hello,

    I'm getting all my reports in order for some upcoming bufferpool work & found John Campbell's recommendation from a presentation in my notes to set VPSEQT to 100 for PGSTEAL=NONE pools.  So I have heard from a colleague that they went to 0 – so what is the ROT out there? 100 or 0?

     

    We have tremendously large pools – many that are multiple millions of pages & using large frames, FYI. For example:

     

    -G BUFFERPOOL NAME BP2, BUFFERPOOL ID 2, USE COUNT 7   

    -G BUFFER POOL SIZE = 3000000 BUFFERS  AUTOSIZE = NO   

      VPSIZE MINIMUM  =         0  VPSIZE MAXIMUM  =         0  

      ALLOCATED       =   1355411  TO BE DELETED   =         0  

      IN-USE/UPDATED  =   1349011  OVERFLOW ALLOC  =      6400  

    -G PGFIX ATTRIBUTE -                                   

       CURRENT = YES                                            

       PENDING = YES                                            

     PAGE STEALING METHOD -                                     

       CURRENT = NONE                                            

       PENDING = NONE                                           

    -G THRESHOLDS -                                        

      VP SEQUENTIAL    = 40   SP SEQUENTIAL   =  0              

      DEFERRED WRITE   = 30   VERTICAL DEFERRED WRT  =  5,  0   

     

     

    What is the consensus / general practices out in real life land?  As always, your time & consideration is appreciated.

     

    Thanks

    Missy Case

    CSG

     

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  • 2.  RE: pgsteal none - VPSEQT=100 or VPSEQT=0????

    Posted Mar 30, 2022 09:46 AM

    Hi Missy, my recollection is that John's recommendation is about repopulating the BP.  This is because PGSTEAL(NONE) turns off prefetch, except for the initial access.  So if you need to repopulate, you really want prefetch to work, and VPSEQT=100 is a switch to turn that on.  Otherwise VPSEQT means nothing, since PGSTEAL(NONE) is intended for objects that fit entirely in the BP.

    Of course, when sizing your PGSTEAL(NONE) BPs, make sure to leave enough room for REORG in case of schema changes, since you do not want the REORG to use the overflow area.



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    MarkRaderIBM
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