Periodical errors in the event log of a SharePoint 2010 server with the following error event descriptions:
Failure trying to synch site
Old references to non existing content databases in the synchronization job list.
List databases which are not synced for more than two days
stsadm -o sync -listolddatabases 2
Delete old database references from the config db
stsadm -o sync -deleteolddatabases 2