Re: why need to backup undo tablespace?

Can you do this experiment? Make a very small database. Only create traditional tables and indexes (no fancy data types, LOBs, etc.) Do some DMLs. Commit. Full scan tables (select /*+ full */...) to prevent later block cleanout. Cleanly shutdown the database. Backup the database except UNDO tablespace. Try to recover. See if it works.

This is not to encourage you to take this unsupported backup strategy, because even if the test is successful you can't guarantee success in the future. Instead it's just to find out under what conditions UNDO is needed in recovery. I remember a few years ago, Anita Bardeen threw a question on Oracle-L while she was talking about something else. She was wondering why she could never clone a database leaving the rollback tablespace out (not using RMAN), and suspected it could be due to block cleanout, among other things if any. If we can find the exact conditions under which we can skip UNDO in backup, and we can recover successfully without using any undocumented parameters, a Tar and/or feature enhancement can be filed. It obviously would save a lot of time in cloning if we could skip UNDO backup.

Yong Huang Received on Thu Dec 09 2004 - 08:27:07 CST