RE: import question

Hi,
I've never seen anything to suggest that exportijng using DIRECT=Y speeded up subsequent imports. I'd be interested to know if this is really the case but I doubt it. The structure of an export file is exactly the same whatever the DIRECT setting. But I've been wrong before ...

Things I'd suggest would be:

• Optimise your online redos - usual advice; pretty big, raw devices, watch for log switch interval.
• Switch off archivelogging.
• Offline all but one, large rollback segment and specify COMMIT=N to delay commits until the end of each object.
• Postpone index creation until the import has finished. Create indexes after the import is completed using the NOLOGGING option (and maybe in parallel too).
• Make sure that you have BUFFER set large enough. 1M-5M is sensible.
• In the olden days there used to be some benefit in relinking the imp executable to use single-task mode rather than two-task. I haven't tested this recently; can anyone confirm that there's still a benefit?
• separate your I/O. Your DB may already be optimised. But your expoprt file on a different disk again.
• Also you may be able to run parallel import streams - you be the judge; just a thought.

Obviously some of these suggestions may not suit your needs.

Regards,
Mike Hately
Oracle DBA

-----Original Message-----
Sent: 29 July 2002 15:38
To: Multiple recipients of list ORACLE-L

If the Export has been taken with DIRECT = Y, meaning that the SQL Evaluation buffer has to be bypassed then Import would not generate the Redo buffer while Importing back the objects and the relevant data.

While Export it just bypasses the SQL Evaluation buffer,make it faster and directly put things in TTC buffer recognized by Import of Oracle

If that option was not selected, frequent commit would enable the checkpoint more often and thus LGWR writing the buffers to redo logs more often. Enable a buffer size which could be substantial high, so that more number of rows could be extracted from the Export file in an array thus boosting the perf.

Thanks
Vikas Khanna

-----Original Message-----
Sent: Monday, July 29, 2002 5:58 PM
To: Multiple recipients of list ORACLE-L

Hi,

We are importing a large amount of data and uit is generating a huge amount of redo..is there any way of avoiding this- unfortunately this is on an 8.0.6 database??

Any help/advice would be appreciated!!

Rgds

FAwzia  

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