Verify that pbx_exchange and nbemm are running.

Examine the command output, debug logs, and system logs for a more detailed message on the error.

See "Setting Media Manager debug logging to a higher level" in the NetBackup Logging Reference Guide.

Run the tpconfig -d or vmquery -a command to verify that the EMM server is actively running and that it accepts new connections.

For a DA reserve drive request, verify that another host has not already reserved the drive.

For a DA release drive request, verify that the drive is DA reserved by the host requesting the DA release and has not already been released.