DSM/Tape Catalog User's Guide

Tape File Concepts
DSM/Tape Catalog User’s Guide — 520233-008
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Expiration Date for an Incomplete Tape File
The tape file entry for YEAR_END_REPORT stays in the catalog until an operator
removes it with a MEDIACOM DELETE TAPEFILE command or until it reaches an
expiration date assigned later with an ALTER TAPEFILE command.
Expiration Date for an Incomplete Tape File
An application that comes to an abnormal end could produce a tape file that is
somehow incomplete and probably should not be used as input. DSM/TC therefore
uses a different expiration date for the tape file entry.
Instead of using the expiration date or retention period specified in the DEFINE or the
default retention period, DSM/TC uses a default abend retention value, set by an
ALTER MEDIADEFS command for each node in the DSM/TC system. The node
specified by the AVRSYSTEM attribute in your DEFINE is the node whose default
abend retention period is used.
An abend retention value should be a low number of days, if not 0. When 0, the entry
for an incomplete file is marked invalid the next time the clean-up process runs. When
the value is 1 or greater, the entry stays in the catalog that many days, then the next
clean-up run deletes it. The entry has a valid status until the clean-up run, so the
incomplete tape file can be requested for input during that time.
Examples
You decide how things are handled when your application abnormally ends. In these
sample cases, assume an abend retention value of 0:

Instruct the operator to rerun the job. The successful rerun creates a new
generation of the output file. The tape file entry for the incomplete tape file expires
at the next clean-up run.
Use this approach when your application uses dif
ferent file names for the input and
output tape files, and the output tapes are not used by any other application.
If the output tape files are used by other applications, two problems can occur:

The tape file entry for the incomplete file could stay in the catalog almost one
full day after it is created, depending on when the next clean-up run is. Another
application could end up using the incomplete file for input.

After the tape file entry for the incomplete file is automatically deleted, a gap is
left in the generation numbers, which might cause trouble if other applications
refer to a tape file name by absolute generation number.

Instruct the operator to delete the tape file entry for the incomplete tape file with a
DELETE TAPEFILE command before rerunning your job.
Use this approach when the application uses dif
ferent generations of the same
tape file name for the input and output files (reads the current generation and
writes the next generation). If the tape file entry was not deleted before you rerun