RE: Why not *SHRPOOL1?

["Andy Nolen-Parkhouse" <aparkhouse@xxxxxxxxx>]

Steve,

I'm not sure that it would cause thrashing, (where the OS is spending
more energy paging stuff in and out of memory than it is running jobs).
But you have a very valid point about mixing classes.  If half of your
activity levels are allocated to jobs running under the QBATCH class
(default timeslice of 5 seconds), then jobs running under the QINTER
class (default timeslice of 2 seconds) will need to wait longer for an
activity level.  Thus your interactive jobs will suffer a greater lag
when it needs to page into memory.  If I recall correctly, the run
priority level will only have an impact when it comes time to get an
activity level, once the a job has an activity level, it will keep it
until the end of it's timeslice.

Regards,
Andy Nolen-Parkhouse

> On Behalf Of Steve Landess
> Subject: Re: Why not *SHRPOOL1?
> 
> Yes.  You are right.
> 
> If you have different subsystems sharing a memory pool, the jobs
> running
> within the shared memory pool can have different time slice/run
> priority,
> based on the class that was used to start a given job.  Interactive
> jobs
> typically use a short time slice with a low run priority {say
> timeslice(500), runpty(20)}, and batch jobs typically use a longer time
> slice with a higher run priority {say timeslice(5000), runpty(50)}.
> 
> Based on this fact, the point I was trying to make is that it is not a
> good
> practice to have batch jobs _and_ interactive jobs running in the same
> memory pool.  You need to balance the working being performed in a
> given
> memory pool to have jobs that are alike in timeslice/run priority
> running in
> that pool.  This helps prevent system thrashing.
> 
> This goes back to the early days of performance tuning on the
> S/38...I'm
> sure that if you read more about this in the Work Management Guide,
> you'll
> see what I am talking about.  As a matter of fact, I'll go look there
> and
> see if I can't find a reference to forward to you.
> 
> Al - please correct me if I am wrong...
> 
> Steve Landess
> Austin, Texas
> (512) 423-0935