TMF Reference Manual (G06.24+)

TMFCOM Commands
HP NonStop TMF Reference Manual—522418-002
3-69
ALTER CATALOG
current status. The catalog is maintained by the catalog process, which starts when
the START TMF command is issued and stops when the STOP TMF command
completes execution.
The catalog process starts in the same processors as the transaction management
process (TMP), unless otherwise directed by the ALTER PROCESS command.
Attributes that you do not specify remain unchanged. So, if you omit an optional
parameter, one of the following actions takes place:
•
If one or more previous TMFCOM commands (such as an earlier ALTER
CATALOG command) specified the parameter, the value entered in the last of
these commands remains assigned.
•
If no previous TMFCOM command specified the parameter, the originally assigned
default remains assigned.
If you enter a DELETE CATALOG or a DELETE TMF command, the originally
assigned defaults for ALTER CATALOG again take effect when a new catalog is
created.
In the ALTER CATALOG command, the RELEASED ON option is useful if you want to
retain TMF catalog entries for use in archiving dumps that are no longer needed for file
recovery. For example, if you want to retain all audit trails indefinitely, you can use the
TMF catalog in this way to keep track of them. If you use this option and later want to
remove the dumps from the catalog, however, you must manually delete them.
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 found. The
ROUNDROBIN option lets you determine how the tape search is conducted:
•
When ROUNDROBIN is OFF, a 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, 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).
•
When ROUNDROBIN is ON, the catalog process begins its search with the tape
after the one last selected and selects the next available tape. If no available tape
is encountered, the process goes through the list completely before starting over
again. Over time, this method ensures that all scratch tapes are used before any
tape is re-used. In this way, catalog processes distribute tape use over the entire
pool of available tapes, minimizing tape wear throughout the pool. (Tape wear is
especially problematical for customers using tape silos in round-the-clock
operation.) An additional advantage of ROUNDROBIN ON is that data on a tape is
not overwritten until the last possible moment, thereby extending the data-