TMF Operations and Recovery Guide (G06.24+)

Recovery Methods
HP NonStop TMF Operations and Recovery Guide—522417-002
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Displaying Backout Process Activity
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Communication is lost between two nodes accessed by the transaction.
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The primary processor for the disk process of a volume accessed by the
transaction fails while the transaction is active.
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Both the primary and the backup processors for the disk process of any data
volume fail while the transaction is active on that system.
The backout process handles an aborting transaction as follows:
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If the transaction inserted a record, the backout process deletes the record.
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If the transaction deleted a record, the backout process reinserts the record.
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If the transaction modified a record, the backout process restores the record to its
original state.
Displaying Backout Process Activity
TMF normally manages the backout process without your intervention. On NonStop S-
series systems, the TMP always runs four concurrent backout processes on each
system, regardless of the number of processors on the system. These backout
processes are created whenever the START TMF command is issued.
A backout process is named $XBKn, where n is a digit uniquely identifying the
particular process. You can use the TMFCOM STATUS TRANSACTION command to
view the status of transactions being aborted by backout processes.
Changing Backout Process Activity
You can use TMFCOM commands to alter the processor on which the backout process
runs, alter its priority, change its memory allocation, and manually invoke the process
to abort a transaction.
Use the ALTER PROCESS command to run the backout process in a different
processor; however, in most cases, the default processor for the backout process is
adequate (see the TMF Reference Manual for instructions).
The backout process, by default, runs at a priority of 149. However, to ensure that
aborted transactions are quickly removed from the database and that affected records
are thereby available for application access, you can use the ALTER PROCESS
command to raise the backup process to a higher priority (for instance, 180).
On systems with a very large number of data volumes or a large number of files
accessed by a single transaction, the backout process may not be able to perform its
recovery operation with its current memory allocation. If this happens, use the ALTER
Caution. Consider the operations and values described in the following discussion very
carefully, because the basis for them is subject to ongoing change. If such changes were
implemented in TMF since this manual was published with RVU G06.23, they will be described
in TMF Supplement for Limits and Defaults Changed After RVU G06.23. If that Supplement
currently exists, please read it for new information about this topic.