The ‘SQLdm Repository Grooming Timed Out’ alert is triggered when the grooming process of your SQLDM Repository has reached the time out period (180 minutes).
The time out period is typically exceeded when the repository database becomes very large in size. Running a complete reindex of the database should help improve the performance of the grooming process and prevent SQL DM from raising this alert.
To review your grooming settings, go to Tools > Grooming Options.