TMF Planning and Configuration Guide (G06.26+)

HP NonStop TMF Planning and Configuration Guide—522416-005

4-1

Reconfiguring Transaction Limits

Transaction processing is governed by several limits and thresholds that can be

reconfigured online if performance issues arise. This section describes how to

reconfigure these limits and thresholds and explains when you might want to do so.

This section contains the following topics:

To reconfigure transaction limit values, you use the TMFCOM ALTER BEGINTRANS

command.

Controlling Transaction Duration (Autoabort)

The TMF autoabort function automatically backs out transactions if they run longer

than a configurable amount of time. This feature is useful in OLTP environments in

which the transactions are usually short. Long-running transactions are identified and

automatically aborted. If you know that there are going to be long-running

transactions, you can turn off the autoabort function to prevent them from being

automatically aborted.

The time limit used to identify long-running transactions is known as the autoabort

threshold. This threshold specifies the length of time that a transaction can run before

TMF automatically backs it out.

You can turn the autoabort feature on and off and change the value of the autoabort

threshold by using the AUTOABORT option of the ALTER BEGINTRANS command.

Setting the threshold to zero turns off the autoabort function; setting it to a nonzero

value turns it on. By default, the autoabort function is on with a threshold of two hours.

Changes in the autoabort threshold apply only to transactions started after the

autoabort threshold was changed. Therefore, if the autoabort function has been turned

off (set to zero) and then turned on again, the function applies only to new transactions

and not to transactions already in progress.

Topic Page

Controlling Transaction Duration (Autoabort) 4-1

Avoiding Runaway Transactions 4-2

Limits on the Number of Active Transactions 4-2

Memory Usage Limits 4-4

Note. TMF also automatically backs out (aborts) transactions based on master audit-trail

capacity. This feature is not, however, configurable; if it causes transactions to be aborted that

should not be aborted, you must increase audit-trail capacity as described in Increasing Audit-

Trail Capacity on page 3-6.