The storage class for an object determines where an object is written (DB2 table, file system, optical, or tape). Objects can be written to tape using the media type and tape unit name defined in the SETOAM statements in the CBROAMxx member of PARMLIB.

When the storage class indicates the object should reside on optical, objects can be written using any drive in any library associated with the object storage group, using any volume assigned to that storage group, as long as there is enough space to satisfy the request and the volume is write-compatible with the drive. If no group volumes are available, the request is satisfied using a scratch volume residing in a library associated with the object storage group.

When the storage class indicates the object should reside on tape, the object can be written using any volume assigned to that storage group, using the unit name in the tape volume record for allocation of a tape device. If no group volumes are available, the request is satisfied using a scratch volume allocated using the tape unit name specified for that storage group in the SETOAM command in the CBROAMxx member of PARMLIB.

The drive startup threshold is the maximum number of write requests (for optical) or maximum KB of object data (for tape) that can be waiting for each drive that is currently processing write requests for the storage group. If the threshold is specified and then exceeded, an attempt is made to start another drive to process write requests to the storage group.

When the number of free KB on a volume falls below the volume full threshold specified for the storage group, the volume is marked full. Similarly, when the number of free KB on a volume falls below the tape full threshold, the tape volume is marked full. If you specified mark volume full on first write failure, the volume is marked as full the first time an attempt to write an object on the volume fails because not enough space remains on the volume.

See z/OS DFSMS OAM Planning, Installation, and Storage Administration Guide for Object Support for more information about writing objects.