DSM/Tape Catalog User's Guide

Introduction to DSM/TC
DSM/Tape Catalog User’s Guide — 520233-008
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The CLASS TAPECATALOG DEFINE
created and then reach the end of their retention period. For more information on
retention periods, see File Retention Period on page 2-6.
As the entries expire, they are marked invalid. Instead of being removed at the next
clean-up run, they stay in the catalog until the last tape file on the volume set expires.
They are all deleted at the next clean-up run. This also means that none of the tapes in
the volume set can be used as scratch tapes until all the tape files have expired.
A tape file entry leaves the file catalog in these ways:

The date representing the end of a tape file’s retention period is reached. On that
day, the entry is deemed expired, and its status is changed to invalid. It is
physically removed at a later clean-up run. See
Tape File Expiration on page 2-10.

An operator uses the DELETE TAPEFILE command to mark an entry for
subsequent removal, regardless of whether it expired.
When more than one tape file is written to a volume set, an invalid tape file entry
remains in a file catalog longer than the next clean-up run. A tape file entry is created
for each file, but the entries can have different retention periods specified by their
DEFINEs. Thus, the tape files expire on different dates.
How Disk File Entries Leave the File Catalog
A disk file entry leaves the file catalog in these ways:

When the tape file entry for a set of disk file entries expires, the tape file entry and
but its disk file entries stay valid. They are physically removed at a later clean-up
run when the corresponding tape file entries are removed.

To give a disk file entry an invalid status, the operator uses the ALTER DISKFILE
command. The invalid entry physically remains in the catalog until its tape file entry
expires, but the entry does not exist to DSM/TC.
Multiple File Catalogs
There is no restriction on having multiple file catalogs. Most DSM/TC systems have
one file catalog per node. Multiple file catalogs can be necessary when:

Different security levels are required for the file catalogs.

Keeping all tape file entries in one NonStop SQL/MP database would take up too
much disk space.

The tapes and files of application user groups need to be physically separate.
The CLASS TAPECATALOG DEFINE
An application uses a CLASS TAPECATALOG DEFINE to:

Request scratch tapes for new tape files

Request cataloging of new tape files