I recently ran into yet another issue, where the error message had absolutely no relation to the final solution. When trying to back up a database, we were getting the following error:

Msg 18273, Level 16, State 1, Line 1

Could not clear 'DIFFERENTIAL' bitmap in database 'RS_newTempDB' because of error 9002. As a result, the differential or bulk-logged bitmap overstates the amount of change that will occur with the next differential or log backup. This discrepancy might slow down later differential or log backup operations and

cause the backup sets to be larger than necessary. Typically, the cause of this error is insufficient resources. Investigate the failure and resolve the cause. If the error

occurred on a data backup, consider taking a data backup to create a new base for future differential backups.

When checking the database properties, I noticed that the log file for the DB was just 504 KB in size, and it’s autogrowth was set to 1 percent. Now, since I had seen issues with keeping the autogrowth for log files low in the past (the famous VLF���s issue, which impacts startup and recovery of the DB), I suggested that we increase it. We set the Autogrowth to something like 100 MB, and voila, the backup completed successfully.

Hope this helps someone.