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

   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