LTXHWM configuration parameter

Use the LTXHWM configuration parameter to specify the long-transaction high-watermark. The long-transaction high-watermark is the percentage of available log space that, when filled, triggers the database server to check for a long transaction.

onconfig.std value: LTXHWM 70
if not present: 80 (if DYNAMIC_LOGS is set to 1 or 2) 50 (if DYNAMIC_LOGS is set to 0)
values: 1 - 100
units: Percent
takes effect: After you edit your onconfig file and restart the database server.; When you reset the value dynamically in your onconfig file by running the onmode -wf command.; When you reset the value in memory by running the onmode -wm command.

Usage

When the logical-log space reaches the LTXHWM threshold, the database server starts rolling back the transaction. If you decrease the LTXHWM value, increase the size or number of log files to make rollbacks less likely.

If DYNAMIC_LOGS is set to 1 or 2, the database server can add a sufficient number of log files to complete the transactions or to prevent rollbacks from hanging when you have long transactions.

If you do not want too many logical logs to be added, LTXHWM should be set to a smaller value (around 60). If dynamic logging is turned off (DYNAMIC_LOGS = 0), LTXHWM should be set lower (around 50) to avoid running out of logical space.

Warning: If you set both LTXHWM and LTXEHWM to 100, long transactions are never aborted. Although you can use this configuration to your advantage, you should set LTXHWM to below 100 for normal database server operations.

If you set LTXHWM to 100, the database server issues a warning message:

LTXHWM is set to 100%. This long transaction high water mark 
will never be reached. Transactions will not be aborted automatically 
by the server, regardless of their length.

If the transaction hangs, follow the instructions for recovering from a long transaction hang, in the chapter on managing logical-log files in the IBM® Informix Administrator's Guide.