Defining performance objectives

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. 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.