IBM z13s, Technical Manual

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Chapter 12. Performance
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application-owning regions (AORs) or batch initiators) that are needed to support a workload.
This factor always has existed, but its sensitivity is higher with the current high frequency
microprocessors. Spreading the same workload over more address spaces than necessary
can raise a workload’s RNI. This increase occurs because the working set of instructions and
data from each address space increases the competition for the processor caches.
Tuning to reduce the number of simultaneously active address spaces to the correct number
that is needed to support a workload can reduce RNI and improve performance. In the LSPR,
the number of address spaces for each processor type and
n-way configuration is tuned to be
consistent with what is needed to support the workload. Therefore, the LSPR workload
capacity ratios reflect a presumed level of software configuration tuning. Retuning the
software configuration of a production workload as it moves to a larger or faster processor
might be needed to achieve the published LSPR ratios.
12.5 LSPR workload categories based on relative nest intensity
A workload’s RNI is the most influential factor in determining workload performance. Other
more traditional factors, such as application type or I/O rate, have RNI tendencies. However, it
is the net RNI of the workload that is the underlying factor in determining the workload’s
capacity performance. The LSPR now runs various combinations of former workload
primitives, such as CICS, DB2, IMS, OSAM, VSAM, WebSphere, COBOL, and utilities, to
produce capacity curves that span the typical range of RNI.
Three new workload categories are represented in the LSPR tables:
򐂰
LOW
(relative nest intensity)
A workload category that represents light use of the memory hierarchy. This category is
similar to past high-scaling primitives.
򐂰
AVERAGE
(relative nest intensity)
A workload category that represents average use of the memory hierarchy. This category
is similar to the past LoIO-mix workload, and is expected to represent most production
workloads.
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HIGH
(relative nest intensity)
A workload category that represents a heavy use of the memory hierarchy. This category
is similar to the past TI-mix workload.
These categories are based on the RNI. The RNI is influenced by many variables, such as
application type, I/O rate, application mix, processor usage, data reference patterns, LPAR
configuration, and the software configuration that is running. CPU MF data can be collected
by z/OS System Measurement Facility on SMF 113 records.