RE: Strange report from 'vmstat'

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Sonja,
The 'fre' column is not exactly as it appears. It appears to show free RAM memory pages at 4K each. However pages are not given back to the fre list until needed. In particular when the system uses large amounts of memory from for I/O caching then these pages are given back only when the free list is getting empty.
The sum of the 'avm' and 'fre' columns do not need to add up to the real memory size of the machine. (roughly transcribed from the AIX Survival Guide)

What exactly is the problem you have identified here?

John

        -----Original Message-----
        From:   Sonja Sehovic [mailto:sonja.sehovic_at_pbz.hr]
        Sent:   02 May 2001 15:20
        To:     Multiple recipients of list ORACLE-L
        Subject:        Strange report from 'vmstat'

        Hi all!
        Oracle 8.1.7 on AIX (8GB RAM (+ swap space 9GB)).
        It concerns AIX memory 'problem'.               
        When I issue vmstat command, we got following result:

        /u01/app/oracle/product/8.1.7.>vmstat 2 4
        kthr     memory             page              faults        cpu
        ----- ----------- ------------------------ ------------ -----------
         r  b   avm   fre  re  pi  po  fr   sr  cy  in   sy  cs us sy id wa
         0  0 580556   554   0   0   0  14   34   0 126  137  63 11  5 82  1
         0  2 580556   549   0   0   0   0    0   0 708  527 206  0  0 99  0
         0  2 580557   548   0   0   0   0    0   0 829 99854 421  2 10 88
0
         0  2 580557   548   0   0   0   0    0   0 637  111  35  0  0 99  0
         
        Analysing this output, it seams that we have cca 2GB RAM (example:


(580557 +

        548)* 4096 = 2,2 GB), while we expected min 8GB.
        This gap between 8GB and output from vmstat report, increases in
time. 
        The question is if our calculation was right, is this the right way
to
        analyse this at all?
        Maybe it is important to say, that our Oracle is installed on OFA
using data
        files, max size 2GB, in same volume group(not on raw devices).
        Do you know of any AIX memory problems which can manifests as
mentioned
        above?

        TIA,
                Sonja

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        Author: =?iso-8859-2?Q?Sonja_=A9ehovi=E6?=
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Author: Hallas, John
  INET: HallasJ_at_logicae.com

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