Oracle-L: RE: Slow Inserts

From: Cary Millsap <cary.millsap_at_hotsos.com>
Date: Fri, 15 Nov 2002 11:28:34 -0800
Message-ID: <F001.005049E2.20021115112834@fatcity.com>

And a note: Using bind variables is a necessary step but not a sufficient step toward eliminating parse CALLS. Using bind variables will only reduce the number of misses in the library cache ("parse count (hard)").

If the application still puts the parse call inside a loop, it still gets the "parse once per execute" behavior shown in the trace file. When the application says "parse" ("prepare" or whatever), the Oracle kernel will parse (unless something on the client side stops the call from going to SQL*Net).

See "Scaling applications to massive user counts" at www.hotsos.com/catalog.

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com

Upcoming events:

- Hotsos Clinic, Dec 9-11 Honolulu
- 2003 Hotsos Symposium on OracleR System Performance, Feb 9-12 Dallas
- Jonathan Lewis' Optimising Oracle, Nov 19-21 Dallas

-----Original Message-----
Baumgartel
Sent: Friday, November 15, 2002 11:20 AM To: Multiple recipients of list ORACLE-L

The Parse statistics are what caught my eye. The statement is being parsed once per execution, which is puzzling because it does use bind variables. Of more concern, though, is the difference between CPU and elapsed times for the parsing, indicating that there is a lot of waiting going on. I'd suggest looking at v$session_event to see what are the top wait events for the session.

break on sid
col event format a30
set pages 99
select se.event, se.total_waits,

se.time_waited, se.average_wait
from v$session s, v$session_event se
where s.sid = se.sid
and s.username is not null
and s.sid = &sid
order by se.time_waited
/
Run this before and after executing the insert statement, and compute the delta for each wait event seen.

HTH Paul Baumgartel

JApplewhite_at_austin.isd.tenet.edu wrote:
>
> Oracle 8.1.7.0.0 on Win2k (4 CPU, 4GB RAM)
>
> A 3rd Party app. is experiencing very slow performance on one of our
> databases. I think I've nailed it down to slow, row-at-a-time
> inserts.
> The same app. performs very fast on another DB with LMTs. After
> switching
> the tables and indexes in the slow DB to LMT, we still have slow
> performance.
>
> The extract from the SQL_Trace below is the slow statement. It
> actually
> takes about an hour to insert a few hundred rows. You can watch the
> trace
> file slowly grow with executions of this statement.
>
> There is only one User hitting this table (with its single index).
> The
> table is initially empty, so it's not extending.
>
> Anybody have any ideas as to the cause of this slow Insert activity?
>
> BTW, I ran BStat and EStat during this time and nothing jumps out at
> me.
> Also, we ran it with CHOOSE (and fresh statistics) - same slowness.
>
>

> INSERT INTO "SASI"."W_ENROLL" ("SCHOOLNUMBER" ,"STULINK" ,"FROMDATE"
> ,
> "TODATE" ,"GRADE" ,"TRACK" ,"PEIMSTRACK" ,"PEIMSSCHOOLNUMBER" ,
> "ADAELIGIBILITYCODE" ,"ISENTERDATE" )
> VALUES
> (:1, :2, :3, :4, :5, :6, :7, :8, :9, :10)
>
> call count cpu elapsed disk query current
> rows
> ------- ------ -------- ---------- ---------- ---------- ----------
> ----------
> Parse 2735 5.88 30.00 0 0 0
> 0
> Execute 2735 1.16 1.24 3 2779 8571
> 2735
> Fetch 0 0.00 0.00 0 0 0
> 0
> ------- ------ -------- ---------- ---------- ---------- ----------
> ----------
> total 5470 7.04 31.24 3 2779 8571
> 2735
>
> Misses in library cache during parse: 0
> Optimizer goal: RULE
> Parsing user id: 399 (TXSRC)
>
> Rows Execution Plan
> ------- ---------------------------------------------------
> 0 INSERT STATEMENT GOAL: RULE
>

>
> TIA.
>
> Jack C. Applewhite
> Database Administrator
> Austin Independent School District
> Austin, Texas
> 512.414.9715 (wk)
> 512.935.5929 (pager)
> JApplewhite_at_austin.isd.tenet.edu
>
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author:
> INET: JApplewhite_at_austin.isd.tenet.edu
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Paul Baumgartel
  INET: treegarden_at_yahoo.com

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-- 
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-- 
Author: Cary Millsap
  INET: cary.millsap_at_hotsos.com

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Received on Fri Nov 15 2002 - 13:28:34 CST