These are the parameters which are in effect only if SMS is enabled in Z/OS Environment. These parameters of storage management subsystem(SMS) helps in simplifying JCLs, i.e., the JCL takes predefined values instead of the programmer keying in the value of DD parameters like UNIT, VOL, LRECL, RECF and others. Most of the parameters are defined by the Z/OS administrator.
To start with, we have taken a sample file and pressed ‘I’ in command line and it displays the value like
Just by looking into the picture, we can understand that Management Class, Storage Class and Data class are three main parameters. Under Storage class we have Volume Serial and Device type and under Data Class, we have the dataset characteristic like RECFM, LRECL etc. Let’s go into more details with each category.
Management Class:
MGMTCLAS is given when defining a new dataset on a system. As evident from the name, it manages the dataset in terms of the following(there are others as well):
1. Migration of inactive datasets to archival storage.
2. Delete datasets where the retention period has expired.
3. Release of allocated but unused space in dataset.
Data class Parameter:
The DATACLAS parameter provides the dataset characteristics like the Record organization (RECORG), Record format (RECFM), Record length (LRECL).For VSAM data sets (IMBED or REPLICATE, CISIZE, FREESPACE, SHAREOPTIONS). Using the Dataclass parameter frees the programmer to code all these values in the JCL DD statement.
However, the values derived from the DATACLAS parameters can be overridden by values provided in the JCL parameters coded on the same DD statement.
As seen below, using such standard values results in clean JCL. There are no values keyed in to define the output dataset.
So, how do you define these standards and how does MVS interpret the values? The answer is ACS Routine. The ACS routines are written using the ACS language. Ideally there are four routines one for data class, storage class, management class, and storage group.
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