There is a little known bug with archival style transactional logging that can cause major problems with Domino servers. While IBM claimed to fix this with 5.0.10, there have been many reports of it still not working in later releases, including ND6.
The problem is keeping your active log extents to a number under 70. If you have more than 70 active (not backed up) log extents (*.TXN files), it is likely that your extents will continue to grow until you are out of drive space. Even if you get your backup program to backup and mark the extents as "recyclable", Domino ignores that flag. Instead of reusing the extents that are available, Domino will create new extents. It will do this until you either run out of space on that mount point, or until you shut down the server and delete all extents and the control file. Either of these scenarios could cause corruption of data and create significant downtime.
How do you avoid this? You need to make sure that your transactional log extents are being backed up at an interval that is more frequent than the time frame needed for Domino to cycle through 70 extents. Each extent is 64 MB, so 70 extents equals 4.375 GB. You need to keep tabs on your server to see how often it writes 4 GB of data. This could be anywhere from a few minutes to a few days, depending on your system. Whatever the case may be, I suggest backing up log extents a minimum of 3 times a day, but more frequently if necessary. Doing so could be the difference between a smooth running server and a server on the verge of crashing.
Michael Lazar is a Principal CLP for Domino administration. He is the owner of Illini Consulting and specializes in providing world class Domino administration. Mike offers services in capacity planning, clustering, partitioning, Web administration, S/MIME setup, SMTP configuration, migrations, disaster recovery, and legacy integration. He has been working with Lotus Notes/Domino since 1994.