There are several ways you can customize how users allocate and manage data sets. You can use Storage Management Subsystem, the MVS™ allocation input validation routine, output descriptors, or the Information Center Facilityspace management service. You can write exit routines to customize ALLOCATE command processing. You can set a default data set disposition for the ALLOCATE command in SYS1.PARMLIB member IKJTSOxx.

You can use Storage Management Subsystem to manage your system's data and storage and simplify how users allocate data sets. When users issue the TSO/E ALLOCATE command, they need not be concerned with different storage, data, or management-related operands. Instead, they can use ALLOCATE operands that are related to Storage Management Subsystem to define various data set attributes.

The MVS allocation input validation routine (IEFDB401) enables you to monitor each ALLOCATE command. You can check and, if necessary, change information that the user provides on the ALLOCATE command.

An output descriptor specifies processing options for a system output (SYSOUT) data set. You can use output descriptors to eliminate the need for users to specify output-related operands on the ALLOCATE or PRINTDS commands. If an output descriptor has been defined, when a user issues the ALLOCATE command to allocate a system output data set or issues the PRINTDS command, the user can specify the OUTDES operand and the name of an output descriptor instead of specifying output-related operands. You can define output descriptors by naming and coding OUTPUT JCL statements. If you have JES2 installed, you and your installation's users can also use the TSO/E OUTDES command to define output descriptors. TSO/E provides two exits for the OUTDES command that allow you to customize the use of OUTDES.

The Information Center Facilityspace management service manages data set space. It does this when the data set is almost full by either compressing the data set or by reallocating a larger data set. It can also allocate a data set that does not exist. This service is available to not only the Information Center Facility, but to anyone who wants to use it. Parameter values, available in a CLIST, define the parameters that this service uses to manage data sets. You have the option of changing the default parameter values.

TSO/E provides initialization and termination exits that you can use to customize the ALLOCATE command. The initialization exit can restrict users from using the ALLOCATE command, can change operands supplied by the user, or pass the address of a new command buffer. The termination exit can perform clean-up processing, such as releasing storage obtained by the initialization exit.

You can use member IKJTSOxx of SYS1.PARMLIB to set a default value for the data set disposition specified on the ALLOCATE command. You can set the default to SHR or OLD. If a user issues the ALLOCATE command without specifying a data set disposition, the disposition defaults to the setting in IKJTSOxx.

When you set a default data set disposition in IKJTSOxx, you can make it take effect immediately using the PARMLIB command with the UPDATE operand. You can also list the current ALLOCATE default using the LIST operand of PARMLIB.

For information about data set allocation and the space management service, see Customizing how users allocate and manage data sets.