ABCs of z/OS System Programming Volume 3 - IBM Redbooks

5.8 Using data classes
TSO Allocate
ISPF/PDF
Non-System-Managed
Volumes
Figure 5-8 Using data classes
JCL IDCAMS DYNALLOC
ACS
ROUTINE
Allocation
Data
Class
System-Managed
Volumes
Record and Space Attributes
Key Length and Offset
Record Format
Record Length
Record Organization
Space (Primary, Secondary, Avg
Rec, Avg Value)
Volume and VSAM Attributes
Compaction
Control Interval Size
Media Type and Recording
Technology
Percent Free Space
Retention Period or Expiration Date
Share Options (Cross Region,
Cross System)
Volume Count
Data Sets Attributes
Backup-While-Open
Data Set Name Type
Extended Addressability
Extended Format
Initial Load (Speed, Recovery)
Log and Logstream ID
Record Access Bias
Reuse
Space Constrait Relief and Reduce
Space Up to %
Spanned/Nospanned
Using data classes
A data class is a collection of allocation and space attributes that you define. It is used when
data sets are created. You can simplify data set allocation for the users by defining data
classes that contain standard data set allocation attributes. You can use data classes with
both system-managed and non-system-managed data sets. However, a variety of data class
characteristics, like extended format, are only available for system-managed data sets.
Data class attributes define space and data characteristics that are normally specified on JCL
DD statements, TSO/E ALLOCATE command, IDCAMS DEFINE commands, and dynamic
allocation requests. For tape data sets, data class attributes can also specify the type of
cartridge and recording method, and if the data is to be compacted. Users then need only
specify the appropriate data classes to create standardized data sets.
You can assign a data class through:
► The DATACLAS parameter of a JCL DD statement, ALLOCATE or DEFINE commands.
► Data class ACS routine to automatically assign a data class when the data set is being
created. For example, data sets with the low-level qualifiers LIST, LISTING, OUTLIST, or
LINKLIST are usually utility output data sets with similar allocation requirements, and can
all be assigned the same data class.
You can override various data set attributes assigned in the data class, but you cannot
change the data class name assigned through an ACS routine.
Chapter 5. System-managed storage 251