Ready; No idle devices are available

Hi,

My setup UCS(Backup exec)--Nexus 5k--Tape iScalar 500.

When I use backup media as Tape library, am seeing the issue as "Ready; No idle devices are available  ". For the same scenario if I use backup media as disk, the backup operation is successfull.

I can able to see the iScalar500 in my Backup exec installed server. And I configured the robotic library, still am seeing the issue.

Thanks

Boomi