Re: Multi-processor machines.

Viv Bassani wrote:
> 
> We currently have a single processor 50S #2122 running V3R7
> There is a requirement to run a high CPU/IO intensive batch
> job which has a totally dedicated system. We have run the job
> on the 50S and we are achieving around 100 records per hour. As
> this machine is not powerfull enough for the task we now have a
> new option.
> 
A couple of years ago, in an IBM AS/400 Newsletter, was a description on
using data queues to sysnc a disk prefetch for long running batch jobs. 
There were some dramatic reductions in run time.  (based upon the actual
application your mileage may vary).

In a nutshell here is how it works:

Your main program has some sort of primary file it is processing and
doing CHAIN/READ along the way.

In a separate storage pool, you start a prefetch job which also
processes the same file, skips the first record and does the chain(s)
for the second record.  It basicly stays one record ahead of your main
program.  It waits on the data queue to know that your main program is
starting record two so the prefetch starts record three.

The main program benefits by overlapping it's computations with the
prefetch programs disk I/O so that when the main program does a disk
request the record is already in cache.

You can clone the main program, gutting it's calculations, add the data
queue wait and you have the prefetch program.  It might be worth
spending a day giving it a try.

James W. Kilgore
QAPPDSN@ibm.net
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