Re: Out of space
Yes, in fact transaction logs grow large and the process to truncate them and keep them in trim is the backup. The backup writes the data off to another location. But the larger than usual transaction logs use up more of the space in the backup target volume which eventually fails. So the transaction log backups don't have enough space to write to, so they start failing. So now nothing is truncating the transaction logs so they grow and use up their volume (or file size quota). When the transaction logs can't grow anymore the DBMS stops doing stuff.
Or the transaction logs are set to a fixed max size and they hit that before the next periodic log backup.
You need to alert not only on remaining available space, but also on the rate that space is being consumed.