You can use BRARCHIVE to back up the offline redo log files using RMAN, either with the SAP backup library or with an external backup library. This is available starting with SAP Web Application Server Release 6.10.

The advantage is that the data in the offline redo log files during the RMAN backup is checked for internal consistency. You can think of this as a replacement for the missing verification functionality for offline redo log files when using DBVERIFY.