Oracle-L: RE: export with "first rows"

From: John Kanagaraj <john.kanagaraj_at_hds.com>
Date: Thu, 15 Aug 2002 15:03:37 -0800
Message-ID: <F001.004B70D3.20020815150337@fatcity.com>

Ed,

FIRST_ROWS optimizes for 'best response', and the default CHOOSE would have used 'ALL_ROWS' for 'best throughput'. I have never run a Db in 'FIRST_ROWS' - probably because it would always favor NLs over HJs and have a host of other issues. You should _never_ analyze SYS objects - you will find that Export will complete in an hour, but other queries against the DataDictionary would just go on forever... Ideally, you should only set CHOOSE and tune selected Online queries with the FIRST_ROWS to quickly return the first set of rows. Everything else should use the default of ALL_ROWS... John Kanagaraj
Oracle Applications DBA
DB Soft Inc
Work : (408) 970 7002

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-----Original Message-----
Sent: Thursday, August 15, 2002 2:49 PM
To: Multiple recipients of list ORACLE-L

It looks like you have very high water marks and/or high fragmented segments

Waleed

-----Original Message-----
Sent: Thursday, August 15, 2002 5:14 PM
To: Multiple recipients of list ORACLE-L

Hello,

We have the optimizer mode set to "first rows" on our (25gb) database to meet a vendor requirement. When I do an "direct" export, it runs for 6-7 hours.

When I change the optimizer mode to "choose" it runs in around an hour.
It also runs in an hour when I set the the optimizer mode to "first rows", and run stats on the "sys" schema.

I'm curious why this occurs. Has anyone experienced this ? Any ideas why this happens ? Is this normal behavior ? I could not find anything on metalink. thanks.

Oracle 8.1.7.2, aix 4.3.3.

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Author: John Kanagaraj
INET: john.kanagaraj_at_hds.com

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