CA IDMS IUA EIUA

Re:LE options for running under z/OS 1.6

  • 1.  Re:LE options for running under z/OS 1.6

    Posted 03-10-2005 06:25 AM
    Hi,



    We will be testing out z/OS 1.6 in a few months, upgrading from 1.4.
    Does anybody know what LE runtime options are affected and good values
    for input into the new CEEUOPT to be used for RHDCLEFE in our DC-COBOL
    programs?



    Usually Steve Harmeson can answer this question.



    Thanks



    Chris Wood

    Alberta Department of Energy

    CANADA

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    Normal

    Normal
    Files in Cache - A worthwhile feature? My opinion
    "Hi,



    One of the IDMS 16.0 features that seemed very promising was Files In
    Cache. As a shop with a fair amount of batch processing it could reduce
    some of our disk accesses for database areas that are way too big to map
    to DMCL buffers. Most of our batch is run local mode to reduce the
    overhead of journaling.



    I have performed a number of tests and asked questions of CA on how this
    technique works. I have also had jobs monitored to see what action takes
    place 'above the 2Gb bar'.



    It seems that this was mainly made available for online work. This makes
    sense as the access is perfectly random and could put some 'hot' data
    into cache when it could be swapped out of the DMCL buffer. In a local
    mode batch job it seems less likely that a previously accessed database
    page is going to be accessed again though it could happen. One other
    problem is the reporting of cached hits and I have requested a DAR on
    this issue. If you do not have enough 'above the 2Gb bar' memory defined
    to the IDMS job you will get messages but there are no online tools to
    see the if cache was actually in effect, used or not, and BUFFERSTAT,
    for local mode will show 'Cache Hits' if they happen but again you have
    no idea if you are actually using the feature.



    The information I have gained from CA and z/OS manuals is that this
    feature involves the use of the IARV64 macro that can create MEMORY
    OBJECTS of up to 1Mb 'above the 2Gb bar' to place the database pages
    into. Quite rightly IDMS only loads database pages into the MEMORY
    OBJECTS as and when they are required. It does not make sense to load
    over 1Gb of database pages into MEMORY OBJECTS at the start of a job
    when it may not need to access them all.



    If the database pages could be 'pre-loaded', similar to how PREFETCH
    works, then Files In Cache could have benefits in local mode batch jobs
    as well. It does not have to load more than a tracks worth of database
    pages at a time but if access to memory is much better than access to
    the actual disk this could work.



    I have requested a DAR on this with the use of either a SYSIDMS entry or
    an optional apar for local mode use only.



    Just my opinion.



    Thanks for listening



    Chris Wood

    Alberta Department of Energy

    CANADA



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    Normal

    Normal
    Re: Files in Cache - A worthwhile feature? My opinion
    "Chris, a technique that might be useful for CV mode applications is one we
    have used with dataspaces for some time.

    After IDMS backups and IDMS-DC restart, we launch OLQ area sweep queries to
    load affected pages into memory. Since this occurs at a relatively quiet
    time, the queries go fairly quickly and allow subsequent access to benefit
    from pages already loaded in memory.