Before you define your tape library, consider the tape subsystem characteristics of the devices in the tape library and their ability to support media interchange attributes, recording technology modes and media types required to support your tape data.

Related Reading: For more information about media types and recording technology, see z/OS DFSMS OAM Planning, Installation, and Storage Administration Guide for Tape Libraries.

Volumes inserted in the tape library dataserver can automatically be assigned values for recording capability, media type, and compaction with the Entry Default Data Class. Or, you can supply this information in the cartridge entry installation exit or through DFSMSrmm.

Initially, the volumes in your tape library might be scratch volumes, private volumes, or a combination of both types of volumes. Enter the predominant type of use attribute, Private or Scratch, in the Entry Default Use attribute.

Estimate the number of scratch volumes by media type needed on average at all times to ensure that allocations proceed without interruption. When the count of available scratch volumes falls below the scratch threshold, DFSMSdfp sends a message to your console (designated in your tape library definition). The message stays on the console until the available scratch volumes exceed twice the specified threshold.

When you or DFSMShsm eject volumes from the tape library, the volume entry in the tape configuration database can be retained or purged. Use the Eject Default to set this attribute to Keep or Purge based on your requirements. If you expect volumes to be reused in the library, use the default value, Keep, for this attribute.

When you use DFSMSrmm to eject volumes from the tape library, the entry in the tape configuration database is optionally purged. DFSMSrmm has all the information needed to recreate the entries when the volumes are returned for reuse.

Tape drives can be shared between systems. For more information, see Sharing an IODF.