Re: recovery without restoring backup

niy38_at_hotmail.com wrote:
> I have an undo tablespace in "needs recovery"
> status, after I bring down the database and
> bring back in mount state, I tried " recover
> tablespace undo" wtihout restoring backup firstly,
> and it works.
>
> Is this a media recovery ? my memory is we
> have to restore before recover.

It often helps to post version and error numbers, as well as pertinent things like whether the db crashed or was shutdown abort.

There are some very old notes on metalink about this. One says:

"Basically, at crash recovery time, Oracle discovers an outstanding transaction
in the transaction table of the rollback segment specified by the error

message. After the roll forward stage is completed, Oracle then tries to
clear that entry by appling undo, but it fails for some reason.

The following is a list of the most common reasons why a rollback segment is
marked as "NEEDS RECOVERY" (as opposed to "IN USE") under the STATUS column of
the dictionary view DBA_ROLLBACK_SEGS:

1. The object to which the rollback segment needs to apply undo is in a tablespace that was OFFLINEd IMMEDIATE or a datafile that was made OFFLINE. NOTE: An I/O error can cause DBWR to mark a datafile "OFFLINE" automatically.
2. The object that the rollback segment needs to apply undo is corrupted.
3. The rollback segment itself is corrupted."

jg

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