| DBA Nightmare:
In the middle of upgrading a large database, the process fails for various reasons (not enough space, pmon dies, server crash, etc.). You now have to deal with hours of restoring hundreds of GBs.
Oracle claims that it is simple to restart the upgrade without any real problem. We have not found this to be the typical case.
Normally, you are expected to have a full backup of all your tablespaces to be able to recover from such failures.
However, it is possible to revert to your "old" database by altering all tablespaces to "read only" (with the exception of system, undo, and temp).
You need to backup only SYSTEM, UNDO, and the contolfiles and then you will able to recover using the backup controlfile "until cancel" and issuing a resetlogs'.
When planning an upgrade, it may be worthwhile to consider this option of incomplete recovery.
Precaution: practice this procedure before using it in a production environment. |
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