There were a stack of errors overnight in the DB123 database on SQL01, including one horror show error:
Log Name: Application
Date: 5/24/2018 12:49:39 AM
Event ID: 3314
Task Category: Server
During undoing of a logged operation in database ‘DB123’, an error occurred at log record ID (195237:96178:4). Typically, the specific failure is logged previously as an error in the Windows Event Log service. Restore the database or file from a backup, or repair the database.
The catch is that when I checked the server, the database was online.
Read on for root cause analysis and issue correction. This is a good example where jumping to conclusions could lead you down the wrong path and miss the root cause entirely.