TMF Operations and Recovery Guide (G06.24+)

The TMF Catalog
HP NonStop TMF Operations and Recovery Guide—522417-002
6-7
Changing the Catalog Configuration
Determining the Status of a Tape Volume Upon Release
When all of the dumps contained on a tape volume are released, the status of the tape
volume normally changes from assigned to scratch. If you want to change that status
to released instead, specify RELEASED ON in an ALTER CATALOG command, as
follows:
TMF 25> ALTER CATALOG RELEASED ON
When a tape’s status is scratch, the tape can be used for receiving new dumps. If the
status is released, however, the tape is used neither for file recovery nor for receiving
new dumps; this allows you the possibility of using one or more of the dump files on
the tape sometime in the future in a “recover files to timestamp” operation (to do that,
you must periodically issue an INFO DUMPS command and save the output).
For more information on tape states, see Changing the Status of a Tape Volume on
page 6-13.
Changing the Tape Catalog Search Method
Whenever a tape is needed to satisfy a tape request, a TMF catalog process searches
the list of tapes in the catalog, looking for the next available scratch tape. The process
bypasses all tapes that are not available, and uses the first available tape encountered.
By default, the catalog process always starts its search from the beginning of the list.
As a result, the catalog process always uses the lowest-numbered scratch tape
available. Over time, however, this method typically results in lower-numbered tapes
being used often while tapes near the end of the list are used rarely (or perhaps not at
all). Tape wear is of special concern in situations where a high volume of tapes is
consumed, for example, at sites that have tape silos in round-the-clock operation.
You can override the standard catalog-search method so that the catalog process
begins its search at the tape after the last one selected, and chooses the next available
tape. If the process does not find an available tape before it reaches the end of the list,
the process goes to the beginning of the list and continues the search from there.
Over time, this round-robin method ensures that all scratch tapes are used before any
tape is re-used. Thus, the catalog process distributes tape use over the entire pool of
available tapes, minimizing tape wear throughout the pool.
To override the standard catalog-search method so that the search begins at the tape
after the last tape selected, issue the ALTER CATALOG command with the
ROUNDROBIN ON option:
TMF 15> ALTER CATALOG, ROUNDROBIN ON
To return to the standard method, so that the search always begins from the start of the
list, enter the ALTER CATALOG command with the ROUNDROBIN OFF option:
TMF 23> ALTER CATALOG, ROUNDROBIN OFF