Re: Speed up massive delete

Mike,
when I get a chance to do some testing on the dev server I will check the redo log creation. Some preliminary tests show 3 threads for the deletion of the data 19086 rows 1-pk 7-indexes with the indexes as unrecoverable. I then created the indexes as normal and loaded the table with insert into select from and and then deleted from the table and 4 redo's were created. It might have been a partial redo from the insert that increased the number. I will do more complete tests when I can. Thanks,
Ron
ROR mª¿ªm

>>> MHately_at_etech-uk.com 06/28/01 12:42PM >>>

Ron,
I can see why it would save redo generation on direct load inserts. I can't understand why it would save any time on ordinary inserts, updates, deletes or import.
I'm sure that your loads are direct loads and they make use of NOLOGGING/UNRECOVERABLE which is where you'll see the savings. Your original post mentioned that you are saving on your deletes also and I doubt that this is the case.

Joe,
Thanks, that's the same list that I usually produce at times like this.

Cheers to all,
Mike

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|        |          "Ron Rogers" |

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Mike,
 When you insert data into a table redo logs are written for both the data info and the index info. If the index is created as unrecoverable then the redo log and archive log info is not written. That is where the time savings is derived from.
 During my daily load of my tables (approx 200000 rows, 13 tables ,40 + indexes) the redo log generation and archivelog generation has decreased twice fold. Of course you should take a back up of your data and indexes after the work is completed.
Time is saved during the IMP of the data also if the indexes are unrecoverable and or you EXP with index=N.

>>> MHately_at_etech-uk.com 06/28/01 10:24AM >>>

Ron,
How does creating indexes as UNRECOVERABLE save time when you insert data? As far as I'm aware the only operation it will save time on is the initial creation.

Regards,
Mike

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|        |          "Ron Rogers" |

|        |          <RROGERS_at_galo|

|        |          ttery.org>   |

|        |                       |

|        |          06/28/01     |

|        |          02:51 PM     |

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Jack
Drop the indexes first before you do the deletes will save you time by not creating logs for the indexes being deleted. On my large activity files I have created the indexes as "Unrecoverable" saving time when I add data or delete data.
ROR mªÖªm

>>> nlzanen1_at_EY.NL 06/28/01 05:45AM >>>
Hi All,

I have to do some pretty big deletes on a test environment and they are estimated to take for ever.
Are there any options to speed it up?

Jack

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