DSM/Tape Catalog User's Guide

Introduction to DSM/TC
DSM/Tape Catalog User’s Guide — 520233-008
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Volume Catalog
Volume catalog entries stay in the catalog indefinitely. They do not have expiration
dates. These entries represent a magnetic tape in the DSM/TC system for as long as
the tape is usable. During a tape’s usable lifetime, it alternates between being a
scratch tape and a tape containing one or more files.
When a tape is no longer usable (it is damaged, lost, permanently removed, or
discarded), its volume catalog entry is removed with a DELETE TAPEVOLUME
command.
Status Changes
DSM/TC controls the use of a tape for read and write operations based on the status of
the tape’s volume catalog entry. Generally speaking, a tape continuously cycles
through three stages:
1. Available as a scratch tape
The tape is empty, or all it
s files have expired. The tape can be requested as an
output tape.
2. Selected as an output tape
DSM/TC has reserved the tape to satisfy an output tape request.
3. Assigned to a tape file
The tape contains one or more tape files and can be used only as an input tape
unless the tape media will allow more data to be added (if the tape is ANSI, IBM, or
an appendable backup).
These three stages represent six states a volume catalog entry can have. DSM/TC
changes an entry’s status from one state to another based on what is happening to the
tape in real time.
In the first stage (available as a scratch tape), three states are possible:
Scratch The tape was never used, or all its files expired or manually deleted. It is
immediately ready for use as an output tape. For more details on this status, see
Tape Pools on page 1-6.
Released All tape files on the tape expired or manually deleted, but the tape cannot be
use
d as a scratch tape until an operator changes its status to scratch with an
ALTER TAPEVOLUME command. For more details on this status, see
Tape
Pools on page 1-6.
Bad The tape has a physical defect and must not b
e used until the problem is fixed.
This is the only condition that DSM/TC cannot detect. An operator must change
the entry’s status to bad using the ALTER TAPEVOLUME command.