Rather than defining individual tape volumes for use by specific users, installations can predefine scratch pool volumes with tape volume profiles for use by any user. An installation tape librarian can predefine tape volume profiles to RACF® by using the RDEFINE command with the TVTOC operand and optionally, the SINGLEDSN operand. The TVTOC operand indicates that RACF creates a TVTOC the first time the tape is opened for output. The SINGLEDSN operand indicates that the tape volume can contain only one data set.

To predefine tape volumes, the installation tape librarian selects new or newly degaussed tape volumes in the scratch pool for use with RACF tape data set protection. The librarian defines these tape volumes to RACF with a nonautomatic discrete profile by using the RDEFINE command and the TVTOC operand. (If you do not specify the TVTOC operand, the default is NOTVTOC.) RACF puts the user ID of the person who defines the tape volume (presumably the tape librarian) in the access list with ALTER authority. This action gives the librarian complete control over the profile and the tape volume. RACF puts the user ID in the access list with ALTER authority only if SETROPTS ADDCREATOR is in effect. If SETROPTS NOADDCREATOR is in effect, the tape librarian needs to ensure that they are the owner of the profile and should issue the PERMIT command to give themselves ALTER authority if they need to have complete control over the profile and the tape volume.

When the first user creates a tape data set on a predefined tape volume, RACF builds a TVTOC in the tape volume profile and places the user ID of this person in the access list with ALTER authority. If the volume is defined with the SINGLEDSN operand, no one can write additional data sets on the volume. If the volume is not defined with the single-data-set option, only this user (and the tape librarian) can add additional data sets to the volume without further authorization. Other users can add data sets to the volume only if they have been placed in the volume's access list with at least UPDATE authority.

When the tape librarian needs more tape volumes for the scratch pool, the librarian can issue the SEARCH command with the EXPIRES operand to find tape volumes for which the security retention period for all of the data sets is expired (or close to expiring). The librarian can then use the RDELETE and RDEFINE commands to redefine these tape volumes.

Unlike DASD data sets, tape data sets are not deleted. A tape data set exists until it is overwritten by another program or by a utility such as IEHINITT. Specifying DISP=DELETE for a tape data set only causes the data set to be uncataloged if it was cataloged. DISP=DELETE does not remove RACF protection from the data set or delete the data on the tape volume.