When the Arcserve 12.5 backup software tries to format the tapes to start a backup job or even if you manually try and erase the contents of the tape by right-clicking and selecting Erase the software comes back with a "Database Operation Fails" error message.
This is because the Arcserve Admin account does not have permission to the SQL database to read the header of the tape and the solution is 2 fold.
First what you need to check is whether you have configured the correct account as the admin account by
Opening Arcserve --> Server Admin --> Right click the server name and select "CA ARCServe Backup system Account"
On the following screen you see the account details, please make sure that they are correct.
Once that is confirmed open up the SQL Server Managment Studio Express by right clicking and running it as "Administrator" if you are on Windows 2008 and expand the Security folder and then click on Logins and after that verify that the account is present and has the "Sysadmin" server role assigned to it and if not please go ahead and create a new login for the Admin account and give it the appropriate role and the issue should be resolved!