RE: Stuck Query

From: MacGregor, Ian A. <ian_at_SLAC.Stanford.EDU>
Date: Mon, 22 Sep 2003 15:39:59 -0800
Message-ID: <F001.005D0BB6.20030922153959@fatcity.com>

Good catch. It was showing Waited Known Time, and the seconds_in_wait kept increasing. I was fooled by the latter being incremented each time v$session_event was queried. I did run a trace on it to track the waits, but had to kill the session. I've never gotten dbms_system session traces to work. They never return anything even on newly rebooted machines.

Ian MacGregor

-----Original Message-----
Sent: Saturday, September 20, 2003 4:05 AM To: Multiple recipients of list ORACLE-L

Hi!

How do you verify that your session is still waiting on sequential read? From v$session_event? Is the status column saying WAITING there? (if it says WAITED%, then your CPU is doing something else already, and this record in session wait just shows the last wait).

Tanel.
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Saturday, September 20, 2003 12:54 AM

> SQL> describe chanarch_nlc.archive_wave_i
> Name Null? Type
> ----------------------------------------- --------
> ----------------------

---

> PV_ID NUMBER(38)
> TIMESTAMP DATE
> NANOSECS NUMBER(9)
> STAT NUMBER(8)
> SEVR NUMBER(8)
> OSTAT NUMBER(16)
> VALUE

CHANARCH_NLC.INT_VALUES
>
> SQL> describe chanarch_nlc.arch_wave_i
> Name Null? Type
> ----------------------------------------- --------
> ----------------------

---

> PV_ID NUMBER(38)
> TIMESTAMP DATE
> NANOSECS NUMBER(9)
> STAT NUMBER(8)
> SEVR NUMBER(8)
> OSTAT NUMBER(16)
> VALUE

CHANARCH_NLC.INT_VALUES
>
>
>
>
> SQL> describe chanarch_nlc.int_values
> chanarch_nlc.int_values VARRAY(16384) OF NUMBER(38)
>
> Select * from chanarch_nlc.arch_wave_i
> Where pv_id = 433 and
> Timestamp between '18-SEP-2003:13:48:00' AND '18-SEP-2003:13:49:00'
> ORDER BY TIMESTAMP, NANOSECONDS /
>
> Returns 1 row plus the associated varray data in one second
>
> Select * from chanarch_nlc.archive_wave_i
> Where pv_id = 433 and
> Timestamp between '18-SEP-2003:13:48:00' AND '18-SEP-2003:13:49:00'
> ORDER BY TIMESTAMP, NANOSECONDS
>
> Returns 0 rows in about a second
>
> Select * from chanarch_nlc.arch_wave_i
> Where pv_id = 433 and
> Timestamp between '18-SEP-2003:13:48:00' AND '18-SEP-2003:13:49:00'
> Union all Select * from chanarch_nlc.archive_wave_i
> Where pv_id = 433 and
> Timestamp between '18-SEP-2003:13:48:00' AND '18-SEP-2003:13:49:00'
>
> Returns a single row with the varray data in a second
>
> However
>
> Select * from chanarch_nlc.arch_wave_i
> Where pv_id = 433 and
> Timestamp between '18-SEP-2003:13:48:00' AND '18-SEP-2003:13:49:00'
> Union all Select * from chanarch_nlc.archive_wave_i
> Where pv_id = 433 and
> Timestamp between '18-SEP-2003:13:48:00' AND '18-SEP-2003:13:49:00'
> Order by 2,3
>
> Never returns. It waits forever on a sequential dbfile read event of
> one

the files used by the lob segment which contains the varray data for the value column of chanarch_nlc.arch_wave_i. Nothing appears to be blocking the session. The query plan is as one would expect.
>
> Similar queries against different tables with the same structure
> proceed

without incident.
>
> Ian MacGregor
> Stanford Linear Accelerator Center
> ian_at_SLAC.Stanford.edu
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: MacGregor, Ian A.
> INET: ian_at_SLAC.Stanford.EDU
>
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: MacGregor, Ian A.
  INET: ian_at_SLAC.Stanford.EDU

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San Diego, California        -- Mailing list and web hosting services
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Received on Mon Sep 22 2003 - 18:39:59 CDT