RMAN netbackup Proxy Copy Snapshot

Does anyone have a good link to documentation on using RMAN Proxy Copies with Veritas snapshots? The Netbackup documentation seems lacking, both the Advanced Client and Netbackup for Oracle guide. We're running Oracle 10.2.0.1.0 and Netbackup 6.0.

What appears to happen when I run a backup using nbu_snap is the backup goes straight to tape, which means all the tablespaces are in backup mode for the duration of all the backup.

What I'd like is the backup to go to cache then separately go to tape. This would cut the amount of time the tablespaces are in backup mode.

If there's a best practices guide or any other links people have found helpful it would be appreciated. What we'll likely do if we can't find this is run through the options and see how they really work.

Thx, Dave

--
http://www.freelists.org/webpage/oracle-l