BE2012 only uses 2 tape drives in Virtual Tape Library.

Yesterday, the Symantec support called me and tried to figure out what was happening. 

As troubleshoot with Symantec support, we finally deleted the VTL in data domain, restarted the services and tried to backup again. Sadly, the result still the same. Then he gathered the log for further investigation.

After disconnected the line with Symantec support, I found that he did not cancel the testing backup jobs before deleting the VTL in data domain. Hence, BE2012 reported an error message for some active jobs in the tape drives which were not existing.

And none of backup jobs can be started, all in "Queued" states. (I guessed the last 2 available tapes drives were occupied by the testing backup job.)

Unfortunately, that was after office hour!!!!  I stayed in office over time for troubleshoot by myself...

And finally I had to logon to Database level to delete the orphan entries in "Device" table of BEDB database, and restarted the services.

Finally BE2012 now can use all the tape drives in VTL now. I hope this is the last time I call for Symantec....