2. PERFORMANCE REPORTING ANALYSIS › 2.7 Graphic Analysis › 2.7.5 Paging Graphs › 2.7.5.5 Demand Page Rates by Workload Type-Bar Chart

2.7.5.5 Demand Page Rates by Workload Type-Bar Chart

GRAPHIC RESULTS

This graphic analysis provides a stacked vertical bar chart
of demand page rates separated by user defined workload
types.  Each defined workload for which there is data is
shown as a separate segment on each bar.

ANALYSIS GUIDELINES

If demand paging exists, this chart will show which workloads
are experiencing the page faults.

Additional information can be obtained by looking at paging
response times.  The I/O response time multiplied by the
number of page faults per second per workload type shows the
impact this paging is having on each workload type.  Dividing
this number by the average MVS multiprogramming level for a
workload would give you an estimate of the impact that an
individual user or job would experience.

Workloads that offer transaction reporting can provide
additional insight into the impact of paging, particularly
slow paging, upon these workloads.  The portion of the
transaction response time caused by paging could be estimated
by calculating the number of demand pages per transaction and
multiplying the result by the paging response time.

You should understand the behavior of the various workload
types when demand paging occurs.  With a workload like TSO,
where each user is placed in a unique address space, when one
user suffers a page fault, the remaining users continue
processing, since MVS is managing their address spaces
independently.  In contrast, when a transaction processing
address space like CICS experiences a page fault, the impact
of MVS halting activity in the address space until the page
fault is resolved can be much greater, since the entire MVS
task in the CICS address space will go dormant until the page
fault is resolved.  This has the potential for halting all
users that CICS is multitasking at that moment.  Only I/O
activity in progress for active users will continue.

The detailed behavior of the paging subsystem can be further
analyzed using the Auxiliary Storage Management analysis
reports described in Section 2.3.

SPECIAL CONSIDERATIONS

If you do not provide a workload description, as shown in
Section 2.7.6.3, each performance group or service class will
be treated as a separate workload.  Further, if you choose to
use report performance groups (rather than control groups),
or report service classes (rather than standard classes),
overlapping resource utilization of such groups or classes
will tend to overstate actual utilization, and should only be
done with a full understanding of the impact on the resulting
analysis.