When a media server is decommisioned b4 removing from Netbackup , plz follow the below steps to make the setup stable once again.
Step 1 : go to server host properties & delete the media server name in the “Media server” List & also in the “server” list.
Step 2. Remove the storage unit which belongs to the particular decomissioned media
Step 3 : stop all the services then, Go to \install path\volmgr\database.
Rename the below files. globdb, robtic_def & ltdevis to .old
go to misc folder & delete all the files except the robotic_def directory.
get inside to this robotic_def dir & delete the files.
Step 4. start all the netbackup services
Open cmd promt & go to volmgr\bin dir
type
vmglob -set_gdbhost
Step 5. go to configure storage devices wizard. you can still see the decommisioned media server entry checkbox.
Delete the decomissioned media server entry alone & discover the conf storage device for the remaining servers
Now u will be able to run bpmedialist without any issues. Some of the tapes will show DBBackup status. You can bring them to scratch or secure the data. (solution given in previously for other person). run thru the forum for this.
This is the solution for ur query & nothing more u need.
Thank’s to Ranjith Kumar. J for the article..
SAIFUL AZIZ's BLOG 
If you decommission a server incorrectly, then add it back and you cannot retreive data from the tapes, what’s the fix for that?
I have critical data I need to restore from those tapes, but because the server wasn’t decommissioned properly, we haven’t been able to inventory the tapes in order to restore the data.
Try to remove the tapes from NetBackup and then run an import.
step 1:
http://seer.support.veritas.com/docs/208420.htm
How to manually remove a tape completely from NetBackup/Media Manager.
step 2:
start an import procedure using the wizard
Dear Aziz,
I just got to know , a very quick and great new tool for decommissioning Media Server , please check the below mentioned link .
NetBackup Media Server Decommissioning Tool now for 6.5.3 to 7.0
https://www-secure.symantec.com/connect/forums/netbackup-decommissioning-media-server-tool-now-653-654-and-655
DOCUMENTATION and DOWNLOAD: How to use Symantec’s NetBackup Media Server Decommissioning Tool for NetBackup 7.0
http://www.symantec.com/business/support/index?page=content&id=TECH130438&locale=en_us
Thanks ,
Adeel Mahmood
kuwait
Darryl Morning, u can move the mediadb into master server it self:
bpmedia:
-freeze|-unfreeze|-suspend|-unsuspend -m [-h ] [-v]
-movedb -m -newserver
[-newsvr_group ] [-oldserver ] [-v]
-movedb -allvolumes -newserver -oldserver [-v]