hi Patrick,
Symantec consultant gives me the following solution, i tried it and it works:
 
1.      Check for corruption :

# strings volDB | head -1

This will return the volDB version, which will be either volDB004 or volDB005.

Find the size of volDB:

# ls -l /usr/openv/volmgr/database/volDB

Subtract eight bytes from the size (the volDB header is eight bytes).

Then divide by 596 for volDB version volDB004, or divide by 660 for volDB 
version volDB005.

If the result is a whole number, then the database is intact.
If the result is not a whole number, then it is corrupt.

2.      Use the procedure below to recover a corrupt volDB:

1. Shut down the vmd process if it is running:
/usr/openv/volmgr/bin/vmctrldbm -t

2. Move volDB to volDB.old:
mv /usr/openv/volmgr/database/volDB /usr/openv/volmgr/database/volDB.old

3. Start vmd
/usr/openv/volmgr/bin/vmd
This creates a new empty volume database volDB (size = 8 bytes)

4. Run the command
/usr/openv/volmgr/bin/vmdb_compact
This reads records from volDB.old, and inserts them into a new volDB.

5.  Use the UNIX strings command on both the volDB and volDB.old, redirecting 
the output to files (instead of to the screen). Compare the two output files to 
determine if any media has not been transferred to the new volume database. If 
there are pieces of media that have not gone across to the new volDB, then they 
will need to be re-added using Media Manager.
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