Last week I got some complaints about user profile information not being synchronized to other sites in a SharePoint 2007 environment. After some investigation I found the following error in the ULS log:
<date> <time> OWSTIMER.EXE (0x0864) 0x08A4 SharePoint Portal Server User Profiles 8zzy Medium Aborting sweepsynch for guid instance <GUID> due to null or non-online content database
After configuring the database as Ready again, the profile information synchronization resumed again.
If you put you content database off-line, SharePoint is still able to access it but it will not create new site collections. Because were creating new site collections, which we wanted created in a specific database we put all databases (except for that specific one) on off-line. As it turned out, the downside of this is that SharePoint is unable to synchronized the user profile information to databases that are off-line.