Informix

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  • 1.  What units do 'buffers' use in BUFFERPOOL?

    Posted Thu March 14, 2024 08:54 AM

    Hi,

    IBM Informix Dynamic Server Version 11.70.FC5XE

    I'm a little bit confused with measurement of buffers of BUFFERPOOL.

    BUFFERPOOL      size=16K,buffers=625000,lrus=500,lru_min_dirty=2.00,lru_max_dirty=5.00

    On the one hand, the docs declare it uses the OS page size (4K in AIX),

    Each buffer is the size of the operating system page.

    On the other hand, `onstat -b` shows the expected total and size,

    Buffer pool page size: 16384
     126 modified, 625000 total, 1048576 hash buckets, 16384 buffer size

    So, where the truth lies, how to interpret the output of `onstat -b`?



    ------------------------------
    Sincerely,
    Dennis
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  • 2.  RE: What units do 'buffers' use in BUFFERPOOL?

    IBM Champion
    Posted Thu March 14, 2024 10:17 AM

    That phrase indeed is wrong, at least in this general form.

    A buffer is a buffer for an entire page, each buffer pool's buffer size is that of the page size this bufferpool is for.

    So if you configure 625000 buffers for your 16kB page size buffer pool, you'll get 625000 16kB buffers.



    ------------------------------
    Andreas Legner
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  • 3.  RE: What units do 'buffers' use in BUFFERPOOL?

    Posted Thu March 14, 2024 10:45 AM

    Andreas,

    Thank you for your answer.

    The mistake is repeated in 12.10 and 14.10 docs. I bet it's reproduced in release 15 papers, too.



    ------------------------------
    Sincerely,
    Dennis
    ------------------------------