Set this option if you want the timestamps in the logs to have more granularity. Note that this option is limited by the sub-second precision of your operating system and underlying hardware.

If you set this option to 3 fractional digits, for example, this will produce timestamps to millisecond precision. Here's an example line from the misc log:

2008-07-04 11:10:47.816 #u1     | >> 250 Timestamps changed.

Compared to the default mode of second precision:

2008-07-04 11:10:48 #u1     | >> 250 Timestamps changed.

log-timestamp-fractional-seconds=0
log-timestamp-fractional-seconds=2
log-timestamp-fractional-seconds=3

Recommendation:

# log-timestamp-fractional-seconds= (commented out; defaults to 0)