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High Memory Utilization in AIX 7.1

  • 1.  High Memory Utilization in AIX 7.1

    Posted Mon April 14, 2014 06:19 AM

    Originally posted by: javidnoor


    Hi,

    In bellow snap shot top two screens are of our DB server and bellow two screens are of our application server. In DB it shows that 99% of memory is used and in as it shows 49% is used where in all process which shows that maximum 1Gb memory is not in used. Please check what is the exactly memory usage, and which application is using.

    Thanks

    JN



  • 2.  Re: High Memory Utilization in AIX 7.1

    Posted Tue June 25, 2019 04:48 PM

    Originally posted by: Tarcio Nieri


    I have a similar problem.
    I see in topas, the processes that most consume memory, and as always java is between them. However the amount of memory used by them does not justify the result I see in nmon, which says that more than 90% of memory is being used.



  • 3.  RE: Re: High Memory Utilization in AIX 7.1

    Posted 2 days ago

    As I understand, AIX takes memory that's not used for AIX itself or the application for file caching.
    I use nmon "m".
    For an explanation of the AIX virtual memory manager see Overview of AIX page replacement
    or this Practical Guide to AIX
    For an explanation of some nmon memory values see https://www.stix.id.au/wiki/Tuning_the_AIX_file_caches
    or AIX memory statistics

    To check for memory overcommitment, I check the following values:

    PageSpace shows the usage of the paging spaces

    pages/sec to Paging Space (to File System means normal file I/O that is handled by the memory manager too)

    Page Scans: how often must AIX check to find free pages (higher percentage is bad)
    Page Steals : high number means memory conention (is bad).

    lruable pages: how many pages can be examined by the least recently used scan (high number = good).

    The numclient (jfs2), maxclient (jfs2) values show the usage of memory for file caching.
    As far as I understand, numperm = numclient (JFS2+NFS cache) + client pages (jfs Cache)

    If nmon shows higher values of "to Paging Space", "Page Scans" or "Page Steals", I would go deeper in detail with the mentioned AIX commands.

    BTW: if you find a process "/usr/bin/topasrec", it's the longterm recording of nmon, you will find its output in
    /etc/perf/daily or /var/perf/daily.
    The output must be processed by topasout directly or with parameter -a that generates files for the nmon analyzer
    see https://developer.ibm.com/technologies/systems/articles/au-nmon_analyser/
    with a link to the download site (nmon.sourceforge.net).

    You download and open the files created by topasrec in EXCEL, then longterm usage of memory could be seen (good to detect spikes in the nightshift).



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    Achim Haag
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  • 4.  Re: High Memory Utilization in AIX 7.1

    Posted Tue August 06, 2019 04:21 PM

    Originally posted by: alethad


    javidnoor,

    From what you stated as your question. You are comparing apples and oranges when you look at your DB server and your App server.  Oracle and other DB's always grab all the memory for themselves because  DB's run faster in RAM.  That's all there is to it.  So your DB server will always show 99% memory in use.  Unless you get with your DBA to specifically instruct Oracle not to use all the memory.    Applications are different. Most only take what memory it needs. 

     

    Just my 2 cents unless maybe I misunderstood your question.

    Good luck,

    Aixgirl



  • 5.  RE: High Memory Utilization in AIX 7.1

    Posted 7 days ago
    AIX always has high memory. This link has a short explanation why Power Systems behave that way
    https://unixhealthcheck.com/blog?id=252

    I hope anyone can comment on that blog

    Paging Space is your concern if you're running out of memory.

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    Senen Jr Dimanahan
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