Backup job getting failed

Hi,

We have Backup Exec 2010 R3 which is installed on 2008 R2 server.

We are running jobs on B2D and on tape, B2D jobs are running successfully but jobs which are schedule on tape are getting failed.

And our tape library is going offline very frequently.

Below is the error which is showing in logs.

Drive and media mount requested: 7/30/2014 1:00:00 AM
V-79-57344-33035 - Error - Mount failed.
Physical Volume Library Drive not found.

Job ended: Wednesday, July 30, 2014 at 1:00:01 AM
Completed status: Failed
Final error: 0xe0000f16 - The operation failed to acquire the minimum number of drives and media needed.
Final error category: Job Errors

Could anyone help me to fix this issue.