Oracle-L: RE: direct path read waits

From: DENNIS WILLIAMS <DWILLIAMS_at_LIFETOUCH.COM>
Date: Thu, 20 Feb 2003 12:11:38 -0800
Message-ID: <F001.0055360F.20030220121138@fatcity.com>

Babu

When building an index, there are 3 (at least) tablespaces that matter:

Table tablespace
Temp tablespace for sorting
Index tablespace (could be the same as the table tablespace) Ideally you will have all 3 on separate devices. I suspect for your test cases that sometimes only two devices were involved, which would mean slower performance. Also, increase the SORT_AREA_SIZE parameter either in your session or in init.ora. Then Oracle will need fewer passes to disk during the index build.

Dennis Williams
DBA, 40%OCP, 100% DBA
Lifetouch, Inc.
dwilliams_at_lifetouch.com

-----Original Message-----
Sent: Thursday, February 20, 2003 1:41 PM To: Multiple recipients of list ORACLE-L

All

We are doing some performance testing while moving from one server to another. I was trying to time some index rebuilds and noticed something that I cant explain.

I am rebuilding an index on a 1 million row table. Lets say its on tablespace A and when I rebuild it to tablespace B it does in 33 seconds. I put it back on A and then rebuild it on tablespace C it takes 1 min 40 seconds. The only change here is the target tablespace.

When I set 10046 level 12 and counted time waited (ela column)

>From A - B (33 seconds)

sum of elapsed in "DIRECT PATH READ" = 394 ( i think this is cs)

>From A - C (1 min 40 sec)

sum of elapsed in "DIRECT PATH READ" = 6251

The P1 of all of these waits point to the same file (#4 part of TEMP tablespace)

Why should the change in the target tablespace affect the time taken to read from the TEMP tablespace?

TIA Babu

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Received on Thu Feb 20 2003 - 14:11:38 CST