Re: IMPDP, ORA-1555 and UNDO_RETENTION
- From: Martin Klier <usn@xxxxxxxxx>
- To: "Mark W. Farnham" <mwf@xxxxxxxx>
- Date: Thu, 06 May 2010 16:41:18 +0200
Hi Mark,
thanks a lot for the clarification, and the hint with the indexes.
Regards
Martin
Mark W. Farnham schrieb:
> UNDO_RETENTION is about time, not size. So if the time to complete the impdp
> including the index creation is longer in duration that UNDO_RETENTION, then
> Oracle's RDBMS has been permitted to release rather than extend UNDO once
> that amount of time has gone by, even if the retention column of
> DBA_TABLESPACES for the relevant UNDO tablespace is GUARANTEE.
>
> This, in turn, means that the relevant select may not be "huge," just long
> running. I'm not sure WHY impdp has such a long running query on changing
> underlying data, but making UNDO_RETENTION longer may well preserve this
> information with relatively little addition to total UNDO. Having a small
> UNDO_RETENTION just allows Oracle to skip adding more and re-use the expired
> (that is older than retention and not involved in an active transaction)
> bits of undo.
>
> That said, it seems likely that running impdp without creating the indexes
> and then creating the indexes separately could dramatically decrease the
> time of the impdp run and possibly can provide you with faster completion of
> the overall job, depending on how the indexes are then added.
>
> Regards,
>
> mwf
>
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