If using Archival-Style Transaction Logging and the Transaction Logs are not backed up frequently enough, or if the backup solution fails and does not backup and flag the backed up log extents as free, this can lead to the drive filling up entirely and crashing Domino. We have seen this happen and it's not pleasant, here's a tip to help prevent things from turning that nasty.
Set up an Event Generator to monitor for low disk space on your Transaction Log drive and then to send you an email so you have a chance to sort something out before it fills up and crashes your server. For example, to monitor your E:\ drive you would do the following steps.
Open the events4.nsf (Monitoring Configuration) database and open the "Event Generators" -> "Statistic" view, then click the "New Statistic Event Generator" button.
On the Basics tab, select the server to monitor from the drop-list.
In the "Statistic to Monitor" section, choose "Single instance statistic" and select your drive letter from the drop-list. Choose the "Monitor as a number (bytes)" option. See pic:
On the Threshold tab set it up to generate an Event when "The statistic is LESS THAN the threshhold value", and set it to whatever you are comfortable with. The example will monitor for approximately 5 Gig of freespace.
On the "Other" tab click the "Create a new event handler for this event" button.
Click OK to save the Event Generator when prompted. The Handler Wizard will start up, click next and select the "Mail" option.
That's it! You will now have a corresponding "Event Handler" for that event and if you click on the "By Action" view under Event Handlers you should see a Mail action set to send you an email if ever the E:\ drive gets down to 5 Gig of space (or whatever you set), and you'll have a chance to get the problem corrected.