Database not found

While attempting to run the stsadm -o backup command as the MOSS setup user for the first time in a new environment today, I came across an error message in the application event log:

Event Type:    Error
Event Source:    Windows SharePoint Services 3
Event Category:    Database
Event ID:    3760
Description:
SQL Database 'WSS_Content_APP' on SQL Server instance 'MOSSSQL' not found. Additional error information from SQL Server is included below.

Cannot open database "WSS_Content_APP" requested by the login. The login failed.
Login failed for user 'domain\moss_setup'.

I wasn't careful when I first read the message and only read the first line. As MOSSSQL is actually a SQL Server alias to a physical server and this is the first time I've used aliases, I initially wondered if the backup command or stsadm was unable to deal with alias. That's silly, of course, because I've never told MOSS which physical server is underlies the alias and it only knows about the alias.

I'm not sure exactly how MOSS and SQL together track down the WSS_Content_APP database but the crux of this error message lies in the second part as flagged by SQL Server. In my case, the moss_setup account required access to the content database--but that's another blog post.