if drive is continously down if i up the drive also it will go to down ...
what can i do....
Try deleting the drive from "Devices > Drives" and reconfigure it using the wizard.
If it didn't work then you probably have a physical problem so:
If you cannot perform actions in the drive using robtest or if there is a tape inside the drive that you can't remove from the drive you will need to call your hardware vendor.
I forgot something basic: Try cleaning the drive using your cleaning tape (preferentially a new one).
That means something might be wrong with the drive. NetBackup will down a drive if 3 I/O errors has ocurred in 12 hours. It will also down the drive when certain TapeAlert errors are reported by the drive. Check O/S logs (Event viewer on Windows; syslog on Unix, e.g. /var/adm/messages on Solaris) as well as bptm log on media server. Also run Media/Tape log Report. Filter Severity to exclude Info. This will leave you with Error and Warning log entries. Check the resulting report to see what kind of errors are reported on the drive.
Please also do the following:
Add VERBOSE entry to vm.conf in volmgr folder. Do this on all media servers using this tape drive. Stop/Start NBU device management. This will increase device level logging to O/S logs.
Read p. 88 of NBU Admin Guide II:
A set of TapeAlert conditions are defined that can cause the media in use to be frozen. An additional set of conditions are defined that can cause a drive to be downed. Table 2-16 on page 88 describes the TapeAlert codes..
Supporting Storage Foundation and VCS on Unix and Windows as well as NetBackup on Unix and Windows
Handy NBU Links
Have you maybe replaced it recently?
Try running tpautoconf -report_disc to see if it comes up with any "missing drives"
DOCUMENTATION: How to update NetBackup for a replaced tape drive without deleting and re-adding the drive
"Have you still got the box it came in?"