LTXHWM and LTXEHWM and their effect on logging

The LTXHWM and LTXEHWM configuration parameters define long transaction watermarks.

After the release of the dynamic log file feature, long transaction high watermarks are no longer as critical, because the server does not run out of log space unless you use up the physical disk space available on the system. The LTXHWM parameter still indicates how full the logical log is when the database server starts to check for a possible long transaction and to roll it back. LTXEHWM still indicates the point at which the database server suspends new transaction activity to locate and roll back a long transaction. These events are usually rare, but if they occur, they can indicate a serious problem within an application.

Under normal operations, use the default values for LTXHWM and LTXEHWM. However, you might want to change these default values for one of the following reasons:
  • To allow other transactions to continue update activity (which requires access to the log) during the rollback of a long transaction

    In this case, you increase the value of LTXEHWM to raise the point at which the long transaction rollback has exclusive access to the log.

  • To run scheduled transactions of unknown length, such as large loads that are logged

    In this case, you increase the value of LTXHWM so that the transaction has a chance to complete before it reaches the high watermark.

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