Re: Recovery Question

ame..._at_iwc.net wrote:
> If you place a tablespace into backup mode, then should you not be
able
> to go to the OS level and copy it to a backup location?
>
> We are installing RMAN shortly, but for now, we are a 24x7 shop and
> need a solution. So, I figured placing each tablespace into a hot
> backup mode, copying the database file and then ending the hot
> backup.......

You're obviously unclear on the concept of a hot backup and how it actually allows you to copy live database files.

Once a tablespace is put into backup mode (using "ALTER TABLESPACE <tablespacename> BEGIN BACKUP") the file header stops being updated for any changes made to the dataflie. All changes are written to the redo logs. Updates to tablespaces in backup mode create more than the usual amount of redo because each change causes Oracle to write the entire block rather than just the changed data to the redo log. This is one reason your recovery takes 'forever'. It's alao the reason you can't use a hot backup made outside of RMAN to clone a database. The file header for each file in the tablespace is not updated again until the tablespace is taken out of backup mode with "ALTER TABLESPACE <tablespacename> END BACKUP".

Had you understood the mechanism beforehand you'd not find yourself in this predicament now. Possibly a read through the Backup and Recovery manual, at tahiti.oracle.com, is in order.

David Fitzjarrell Received on Thu Apr 07 2005 - 13:56:16 CDT