DSM/Tape Catalog User's Guide

Tape File Concepts
DSM/Tape Catalog User’s Guide — 520233-008
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File Retention Period
three versions, if MASTER_OUT is the only file in the volume set, version 0 and 1 of
generation 3 will have expired and been deleted.)
File Retention Period
When a tape file is created, it is given an expiration date to define how long to retain
the tape file past its creation date. This date is stored in the file’s tape file entry. Until
the expiration date is reached, the tape file entry has a status of valid, meaning it is
used when DSM/TC is searching for information to satisfy a tape request.
When the expiration date is reached, the tape file entry is given a status of invalid and
is considered expired. Expired entries are not used for inquiries to DSM/TC. Any
request for the tape file of an expired entry is rejected because DSM/TC would not find
an entry matching the tape file name specified in the DEFINE. Expired entries are
marked invalid and are physically removed at a later clean-up run.
The expiration date is stored in both the DSM/TC catalog and the media’s label. You
can use the ALTER TAPEFILE command to change the expiration date in the catalog,
but this does not change the label of the media. If there is a discrepancy between the
expiration date in the label and in the catalog, the information in the catalog is used.
Example
Two tape files are created on January 15, 2001 with the same expiration date of July
15, 2001. In February the operator is instructed to give the tape file entries new
expiration dates with an ALTER TAPEFILE command. This summarizes these events:
Unless the tape file entries are changed again, CALIF_RATES can be used one month
longer than originally intended, and ORE_RA
TES can be used one month less.
Sources of Retention Period and Expiration Date
An expiration date originates from one of:

A TAPECATALOG DEFINE
To specify the chosen date, use the EXPIRA
TION attribute or RETENTION
attribute. (When RETENTION is used, the retention period is converted to an
expiration date.)
You can also have a tape file not expire by specifying RETENTION PERMANENT
for it
s retention period. Such a tape file entry can be given an expiration date later,
Note. If a cataloged labeled tape and its files are used at a site that does not use DSM/TC, the
expiration date in the tape’s label determines whether the tape file has expired.
Tape File Name Creation Date
Expiration Date in 
Tape Label
New Expiration Date in 
Catalog
CALIF_RATES January 15, 2001 July 15, 2001 August 15, 2001
ORE_RATES January 15, 2001 July 15, 2001 June 15, 2001