Re: File Reads

> If we are running a machine with approx 380 mb in the pool where the job
> is running alone would we still get paging problems ?  What is the
> guideline for this?  I remember reading an article some time back about
> "encouraging" the 400 to cache particular files.  Is this still
> available or is the system doing this automatically now?
> 
> We have 512 mb and overnight there are only spool writers and server
> jobs active on the system.

  John, If you have only one task running in the pool you can use
DSPACCGRP (part of performance tools) to fund out how much memory the
task needs.  The rest is available for files and blocking.  380MB is a
great plenty for some serious buffering since it is unlikely that the
batch task is using much more than 1MB for programs.  There is always a
rate of dimishing returns, if blocking 100 records doubles the speed,
200 may only add another 5% or it may add 50% or it may not change at
all, you'll need to experiment.  They key point is when the system is
able to get data from/to disk fast enough to keep the processor(s)
burried. At that point additional buffering is a waste of effort.

  As I mentioned before if you demand 32K of records be blocked, the
system will do it, and with a 512 byte record that would chew up about
16MB.  You can see that in your 380MB pool this is no problem with a
single task, but on a busy system in a tight pool, this could be a
performance dagger.  

  As to your quesion about the system trying to 'cache' files, that is
basically the *CALC option for the pool.  It naturally (because of
single level store) brings in heavily used records but not big chunks of
the file.

  Larry Bolhuis
  Arbor Solutions, Inc
  lbolhui@ibm.net



> 
> John Hall
> Home Sales Co.
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