Re: Fastest access: user space, data area, data queue

Thanks Dave.

Actually, I am putting the object in QTEMP for later processes in the job to 
read and modify. Typically I would use a data area but I was just wondering if 
this is the most efficient. As I said, it probably doesn't make much difference 
but I was just curious.

Albert 

----- Original Message -----
From: "Dave Schnee" <DSchnee@xxxxxxxxxxxxxxxxxxx>
To: midrange-l@xxxxxxxxxxxx
Subject: Re: Fastest access: user space, data area, data queue
Date: Tue, 13 Jun 2006 13:25:54 -0400


    Albert:



    You don't make it clear what you mean by "accessing".  If you need to
    read/increment/update something in a user space or data area, you will
    want to prevent others from doing so at the "same time".  That means
    allocating the object.  The retrieval from or writing to a data queue does
    not use that kind of locking mechanism.



    If you use a user space and do NOT need to lock it, your speed depends
    upon how often you need to get a pointer to the (data part of) the space.
    If it's a "one guy does any updating and many guys read the current
    value", then the user space might be your best bet (only one guy needs to
    do the ALCOBJ/DLCOBJ).  If many guys need to do a read-then-update, you
    need to allow time to locate the object for each part of ALCOBJ, Read,
    change, DLCOBJ - at least for a DTAARA.  For a user space, you may be able
    to get a pointer to the space once then do many cycles of ALCOBJ, read,
    change, DLCOBJ which will only need to locate the object 2 times instead
    of 4.



    A data queue will need 2 rounds of "locate the object" but will also need
    time to get and/or put a message.



    The BEST speed combination if many guys need to ALCOBJ/read/change/DLCOBJ
    is probably the user space.  I had a requirement to have many jobs doing
    just this and I found that the name resolution inherent in the
    ALCOBJ/DLCOBJ took 99% of the time if I used a user space and I could keep
    the pointer to the space between updates.  I was able to use the MI LOCKSL
    and UNLOCKSL interfaces (but only in C, not RPGLE) to get a "system
    pointer" to the user space and save this pointer between retrieval/update
    cycles to save 99% of the time.



    That's not for the faint-of-heart but it was most effective.



    Dave Schnee,

    Barsa Consulting Group, LLC



    -------------  Albert York wrote ----------



    date: Tue, 13 Jun 2006 08:37:47 -0800
    from: "Albert York" <albertyork@xxxxxxxxx>
    subject: Fastest access: user space, data area, data queue

    I was wondering is there is any kind of significant difference in speed
    when accessing a user space, data area, or data queue entry.

    Thanks,

    Albert
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