Explanation:
Lotus Domino purges log.nsf everyday at 4:00 AM.
The Notes.ini settings LOG_PURGE_HOUR changes the log purge hour.

Applies to:
Lotus Domino Server

Default:
4

UI Equivalent:
None

Recommendation:
If your Lotus Domino server workload is not so high at 4:00 AM, do not change the default value.
If the workload is high at that time, (e.g. heavy background agent is running, Domino backup or shutdown is scheduled around the time), Set LOG_PURGE_HOUR so that the purging log.nsf is performed when your Lotus Domino server workload is relatively low.

Syntax:
LOG_PURGE_HOUR = value

value: 0 - 23 (specify 0 - 23 value in 24 hours format, otherwise LOG_PURGE_HOUR is set to 4)


Example:
To change the log purge hour to 10:00 PM, you need to set the value as follows

LOG_PURGE_HOUR=22

Restarts:
To enable the change, you need to restart Lotus Domino Server


References: