Netbackup 8.0 unable to release channel after restore is complete

[farazmajid]

We are taking backup of Oracle 12.0c running on Oracle Linux 7.4, and netbackup agent version is 8.0. Backup is successfully taken through intelligente policy, but while trying to restore this backup to an identical machine with same configration and different IP's at the end when restore is completed it gives error while releasing channel and strangly Netbackup Administration Console show the restore is successfull.

[Marianne]

Channel release is an Oracle function.
You need to troubleshoot rman output.

NBU reports success because it has sent all data to Oracle.

[farazmajid]

We also observed that the last file restored by Netbackup have file size difference, means the file restored on the target machine its size is less then the original one backed up by netbackup. can this be a issue???

[Marianne]

If you run bplist with -l option (command usage in NBU for Oracle Admin Guide), you will see the size of each backed object.
You should be able to compare this in restore logs (probably dbclient and bptm). 

The Troubleshooting section of NBU for Oracle manual will list all the logs that are needed from NBU point of view as well as rman. 
Level 3 NBU logs should suffice.
If you feel that a Support call with Veritas is needed, then ensure you have level 5 logs.
(ONLY enable level 5 logging when you decide to contact Veritas Support.)