TMF Operations and Recovery Guide (G06.24+)

Occasional Operations
HP NonStop TMF Operations and Recovery Guide—522417-002
3-19
Changing the Autoabort Threshold
Setting the autoabort threshold to a non-zero value means that TMF automatically
backs out transactions that exceed the autoabort threshold. By default, the autoabort
threshold is two hours.
Setting the autoabort threshold to 0 turns the autoabort feature off, so that transactions
can run until completion, regardless of the time required. Do not turn off the autoabort
feature unless you are certain that there is enough space in the audit trail to
accommodate the audit-trail files that may be pinned for an extended time while
transactions complete.
Changing the Autoabort Threshold
You can alter the autoabort threshold while TMF is running. When the autoabort
threshold is changed, new transactions become subject to the new autoabort
threshold. However, currently active transactions remain subject to the previously set
autoabort threshold.
To alter the autoabort threshold, use the ALTER BEGINTRANS command; this
command can be issued only by members of the super user group (see the TMF
Reference Manual for instructions). In the following example, the default autoabort
threshold is decreased to one and a half hours:
TMF 64> ALTER BEGINTRANS, AUTOABORT 1 HOUR 30 MINUTES
The new threshold is applied to transactions that begin after the ALTER BEGINTRANS
command is issued.
The value of the TMP process’ node disconnect timer, if modified through the SNOOP
utility, can impact the use of the AUTOABORT option in the ALTER BEGINTRANS
command. The disconnect timer specifies the maximum number of seconds that a
distributed transaction is allowed to exist without receiving any replies from a
participating node; when this time limit expires, the TMP terminates the transaction. If
you use the SNOOP utility to change the disconnect timer value and later issue a
TMFCOM ALTER BEGINTRANS command to set the AUTOABORT timeout
parameter lower than the new disconnect timer value, the ALTER BEGINTRANS
command fails and an error message appears. To correct this situation, you must
either use SNOOP to lower the disconnect timer value and then reenter the ALTER
BEGINTRANS command with the same AUTOABORT timeout value, or reenter the
Caution. TMF aborts any transaction pinning the oldest MAT file if the file is pinned because
of currently active transactions and if audit information is filling 45% or more of the MAT
capacity. Beyond this, however, when the autoabort feature is off (threshold set
to 0), there is no mechanism to abort runaway transactions automatically; if multiple runaway
transactions go unnoticed, they can cumulatively pin many audit-trail files, preventing them
from being recycled and prohibiting the start of new transactions.