Data set resources - allocation

Allocation is the process the system uses to map requests for data sets to available devices and volumes. This topic contains guidance information about the allocation of data set resources. Table 1 shows the relationships between the allocation of resources associated with data sets, such as devices and volumes, and the appropriate JCL or JES statements and parameters.

Table 1. Allocation Task for Requesting Data Set Resources
TASKS FOR REQUESTING DATA SET RESOURCES	STATEMENTS AND PARAMETERS FOR TASK
	JCL statements			JES2 statements	JES3 statements
	DD	OUTPUT JCL	Other JCL	JES2 statements	JES3 statements
Allocation
of device	UNIT STORCLAS		CLASS on JOB (JES3 only)		SETUP and CLASS on //*MAIN
of tape or direct access volume	VOLUME STORCLAS				EXPDTCHK and RINGCHK on //*MAIN
of direct access space	SPACE AVGREC DATACLAS
of virtual I/O	UNIT DSNAME= temporary data set
with deferred volume mounting	DEFER on UNIT
with volume premounting				/*SETUP
dynamic			DYNAMNBR on EXEC

This topic includes the following subtopics related to the allocation of data set resources.

Some of these topics include information that describe the topic from the perspective of whether the resource is SMS-managed or non-SMS-managed.

In this topic, SMS-managed and system-managed are used interchangeably to describe resources that the storage management subsystem (SMS) manages, and with SMS indicates information that applies when SMS is installed and active.

Data sets on system-managed tape library volumes exhibit both system-managed and non-system-managed characteristics. When necessary, data sets on a system-managed tape volume are distinguished from system-managed DASD data sets. Otherwise, the term system-managed data sets refers to both data sets on a system-managed tape volume and system-managed DASD data sets.