DSM/Tape Catalog User's Guide

Introduction to DSM/TC
DSM/Tape Catalog User’s Guide — 520233-008
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Tape Volumes
ALTER TAPEVOLUME command, see the DSM/Tape Catalog Operator Interface
(MEDIACOM) Manual. These rules apply:

When a tape volume of label type BACKUP that resides within an append capable
pool is altered from ASSIGNED to FULL, it is no longer available for use until it is
either returned to ASSIGNED or has been expired.

A tape volume of label type BACKUP that resides within an append capable pool
can be altered from FULL to ASSIGNED only if it was previously used in an
append capable operation, then altered to FULL.

A tape volume set to FULL by the Labeled Tape subsystem cannot be altered until
it expires.
SCRATCH media selection
The criteria for SCRATCH media selection changed for append capable pools. These
rules apply:

The algorithm for nonappendable pools attempts to select the next available
SCRATCH media.

The algorithm for appendable pools:
IF append-capable pool AND append-incapable request THEN
reject request with wrong version error 596
ELSEIF
BEGINELSE
IF append-capable pool AND
first volume in set AND
last used not empty AND
not OPEN real media AND
BACKUP label type THEN
BEGINIF
attempt to select the last used ASSIGNED media
IF not found or tape format wrong THEN 
attempt to select the next available ASSIGNED media
with the right tape format
ELSEIF
attempt to select the next available SCRATCH media
ENDIF
ELSEIF
attempt to select the next available SCRATCH media
ENDELSE
This is true for all scratch media selection from append capable pools except when a
tape file set spans more than one tape volume. In that case, when a tape file set rolls
over to a subsequent tape volume (FILESECTION and VOLINDEX become greater
than one), a SCRATCH media is always selected. This insures that a Backup tape file
set (FILEID or TAPEFILE) that overflows the end of a tape volume never continues
onto the middle of another tape volume.