In the performance objectives fields of the Storage Class Define panel, you can request
millisecond response (MSR) times and indicate the bias of both direct and sequential access data
sets. The fields are:
- Direct Millisecond Response
- Direct Bias
- Sequential Millisecond Response
- Sequential Bias
All of the performance attributes are optional.
If you leave all MSR and
bias fields blank (direct and sequential),
SMS ignores device performance during volume selection. With the introduction
of the IBM® Enterprise Storage Server® (ESS) and large cached controllers, the storage class
MSR value is less significant except as noted below.
Tip: The MSR and bias values you specify
in the storage class can be used to determine how buffers are to be
allocated when system-managed buffering is used for VSAM applications.
To do this, specify a value of
System for
the Record Access
Bias attribute in the data class. This capability applies only to
system-managed VSAM data sets allocated in extended format and accessed
by batch applications. MSR values are also used to cache PDSE members
and HFS files. For guidance on specifying MSR and bias values in the
storage class, see
Processing Techniques in
z/OS DFSMS Using Data Sets.