TMF Operations and Recovery Guide (G06.26+)

Occasional Operations

HP NonStop TMF Operations and Recovery Guide—522417-003

3-20

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

ALTER BEGINTRANS command with an AUTOABORT timeout value higher than

the present disconnect timer value.

The SNOOP utility is provided with the TMF product, and is documented in the file named

$SYSTEM.SYSnn.SNOOPDOC.

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.

Note. This problem occurs only if you change the disconnect timer setting from its default

value (30 seconds); that is, the AUTOABORT timeout value can be set lower than the dis-

connect timer value if the disconnect timer value is not changed from its default.