running WAS on iSeries - Websphere

This is a discussion on running WAS on iSeries - Websphere ; Hi there, Would somebody please tell me is that a right way to run WAS on iSeries? We always experienced the performance issue and don't know how to track it to find out the point of issue. Please sharing your ...

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Thread: running WAS on iSeries

  1. running WAS on iSeries

    Hi there,

    Would somebody please tell me is that a right way to run WAS on
    iSeries? We always experienced the performance issue and don't know how
    to track it to find out the point of issue. Please sharing your
    experence or advice to me!


    Thank you very much,

    Laurence


  2. Re: running WAS on iSeries

    Laurence,

    Without knowing the specification of your iSeries, and the nature of
    the application, it is difficult to offer much advice. However, one
    crucial factor is memory pools. My experience is that you must run WAS
    in a dedicated pool. If you share the pool (for instance if you are
    running WAS in *BASE), the Java heap can get paged out to disk. If this
    happens, the Garbage Collector can struggle to reclaim memory (you will
    see high paging in WRKSYSTS, and busy disks in WRKDSKSTS).
    If your app is running slowly, but the CPU utilisation is not very
    high, this is very likely to be the reason why.

    Hope this helps,

    Walker.


  3. Re: running WAS on iSeries

    HI,

    When WAS is deployed on Windows/Unix-like platforms, the specs will be
    the numbers of CPU, the GHz of CPU, the amount of RAM and so on.

    On AS/400, the legacy applications (e.g. RPG programs) are used to
    evaluate benchmark by CPW. BUT, should it be evaluated by CPW as well
    when WAS is deployed on AS/400? Or just like the stated above?

    In terms of cost/performance, should we deploy the legacy applications
    and WAS solutions on different AS/400? Or mix them in a single large
    machine? Which one is the best deployment way?

    Laurence


  4. Re: running WAS on iSeries

    On the AS/400, CPW is not the best indicator of Java performance, but
    these days there is not a lot else to go on. IBM used to provide CIW
    ratings for comparing Java workload performance across different
    AS/400s, but this has now been dropped.
    CPU numbers, GHz, and RAM are still important on the AS/400, as is L2
    cache. Increasing GHz and L2 cache will give you a bigger payoff for
    Java than it does for legacy (5250) applications. It is worth noting
    that some older small AS/400s had no L2 cache at all.

    For WAS 5.0, IBM recommends a minimum of an 820-2395 (370 CPW, 400 MHz
    and no L2 cache) with 750M RAM per WAS instance if you only want to use
    servlets and JSPs. If you want to use EJBs, the recommendations
    increase to an 820-2396 (950 CPW, 450 MHz and 2M L2 cache) and 1G RAM.
    Bear in mind that these are minimum requirements, and your application
    may require more power.

    We used to run 2 WAS 3.5 servers (each with a relatively small JSP and
    servlet application) on an 820-2395 with 750M RAM per WAS server
    alongside legacy applications with no problems. Currently we run the
    same set-up with WAS 5.0 on an 810 (1020 CPW) with the same RAM, and
    performance is much improved.

    As far as cost/performance goes, what you will have to watch out for is
    your 5250 requirements. An Enterprise Edition (with all CPW available
    for 5250 work) of a large AS/400 can be very costly. If you can
    dedicate a single AS/400 to purely non-5250 work (such as WAS
    applications), you will only need the Standard Edition (no 5250
    capability), which will be much cheaper.

    There are some AS/400 specific WAS settings (such as the
    os400.jit.mmi.threshold) which can have an impact on your application.

    And obviously there are cross-platform WAS settings and application
    design (object caches etc.) which you can change to speed things up on
    any hardware platform.

    Walker.


  5. Re: running WAS on iSeries

    Laurence, two other things you might want to take a look at are the
    Workload Estimator on IBM's website, and PATROL - Predict from BMC.

    Walker.


  6. Re: running WAS on iSeries

    Laurence, two other things you might want to take a look at are the
    Workload Estimator on IBM's website, and PATROL - Predict from BMC.

    Walker.


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