Loss of Undo tablespace

Question

Hello Friends
I am confuse about a snario, please clear it:
What if we loss undo tablespace(data files), and all files remain safe(database in archive log 9i) and the tablespace have some active transactions at the time of failure. My question is that how oracle will recover ? and where the undo data for uncommited transaction will come from at the time of recovery.
Sunil Kumar

Answer 1

You can create new undo tablespace , though, is that there cannot be any active transactions in the Undo segments of the tablespace when it is time to actually drop it. In the case of data file corruption, uncommitted transactions in the database that have data in Undo segments can be extremely troublesome because the existence of any uncommitted transactions will lock the Undo segments holding the data so that they cannot be dropped. This will be evidenced by an "ORA-01548" error if this is attempted. This error, in turn, prevents the drop and recreation of the Undo tablespace, and thus prevents the successful recovery of the database.
To overcome this problem, the transaction tables of the Undo segments can be traced to provide details on transactions that Oracle is trying to recover via rollback and these traces will also identify the objects that Oracle is trying to apply the undo to. Oracle Doc ID: 94114.1 may be referenced to set up a trace on the database startup so that the actual transactions that are locking the Undo segments can be identified and dropped. Dropping objects that contain uncommitted transactions that are holding locks on Undo segments does entail data loss, and the amount of loss depends on how much uncommitted data was in the Undo segments at the point of failure.
Hope this hepls...