Andy Galbraith walks us through a backup issue he experienced recently:
These messages showed that a process of some kind ran just after 9 pm that switched the databases from FULL recovery to SIMPLE and then back again. This broke the LOG recovery chain and required new FULL backups before any LOG backups could succeed, which is why the LOG backup job was failing.
This sort of interesting user behavior is why it’s so important to have automated systems in place to check for issues and, whenever possible, fix them.