You can refer to the troubleshooting guide for more information, but on your master server you can run this bperror command:
So for example, if your backup fails with a status code 71 and you don't know what that means, you can run
/usr/openv/netbackup/bin/admincmd/bperror -S 71
Your output will look like this:
none of the files in the file list exist
The files in the file list did not match any of the files on the client. This error can occur with only one file in the file list and the file cannot be backed up due to an I/O error.