UNDO, Some Discussion

OK, below are issues relating to the undo problems with oracle 9.2.0.3.

Seems as though there are a few bugs. The problem we seem to have is when we do either materialized view refreshes and truncate table type commands.

The problem seems to be that oracle can not create enough undo segments. When running these again, often straight after the failure it works. This generally seems to be the case.

The way undo seems to normally work is that it creates segments when required. There are particular rules around when it grabs new extents, how much space it grabs etc. The smon process is responsible for dropping undo segments that are not required any more. It generally does this every 12 hours. There is an event to stop this from happenning.