Oracle-L: Re: Hanging query puzzle

From: John Shaw <John.Shaw_at_correctionscorp.com>
Date: Wed, 05 Feb 2003 11:09:16 -0800
Message-ID: <F001.00544A5F.20030205110916@fatcity.com>

What version are you running - I have a similar problem on 9.2.0.2 on Solaris 9 that I've had an open tar on since November - Support has finally called up and said other people are having the same kind of problem - especially in regards to parallel processes. I am supposedly getting a test scenario from them to check out. I'll post the results if and when I get any.

>>> ThomasJe_at_tce.com 02/05/03 11:59AM >>>

We have a query from a 3rd-party tool that seems to either run very quick or crawls to a complete stop. We can find no patterns to this behavior. The hang can be experienced even when there are no other

processes active in the database.     Checking waits, we see a db file scattered read. 
SID EVENT                        P1TEXT                     P1 P2TEXT                     P2 P3TEXT                     P3
----- ---------------------------- ------------------ ---------- ------------------ ---------- ------------------ ----------
    1 pmon timer                   duration                  300                             0                             0
   12 slave wait                   msg ptr            5.0440E+17                             0                             0
   13 slave wait                   msg ptr            5.0440E+17                             0                             0
   14 slave wait                   msg ptr            5.0440E+17                             0                             0
   15 slave wait                   msg ptr            5.0440E+17                             0                             0
   28 db file scattered read       file#                      12 block#                  21047 blocks                      2
    5 smon timer                   sleep time                300 failed                      0                             0

Then going to v$sess_io, we see the process is comletely stuck, no activity going on at all, and it's the only active process in the database.
SID BLOCK_GETS CONSISTENT_GETS PHYSICAL_READS BLOCK_CHANGES CONSISTENT_CHANGES

----- ---------- --------------- -------------- ------------- ------------------ 
   28    6233582        60812023       36589516       4076353                115

The query looks like this:
SELECT PRAssignment.*, SRM_RESOURCES.RESOURCE_TYPE FROM PRAssignment, SRM_RESOURCES
WHERE prModTime > TIMESTAMP '2003-02-05 09:23:56.0' AND PRAssignment.prResourceID=SRM_RESOURCES.ID If I check the file/block values for the wait I get the prassignment table. Prassignment has 5K rows while srm_resources has 300 rows. Prassignment also has a LONG RAW column, consequently we see a high chain count, with the result that it's taking up 135 extents to cover those 5K rows. I'm at a loss to explain why we see such inconsistent results with this query. Thoughts? Thanks.

Jeffery D Thomas
DBA
Thomson Information Services
Thomson, Inc.
Email: jeff.thomas_at_thomson.net
Indy DBA Master Documentation available at: http://gkmqp.tce.com/tis_dba
Select 'Indy DBA' then 'DBA Web Pages'

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Author: John Shaw
  INET: John.Shaw_at_correctionscorp.com

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Received on Wed Feb 05 2003 - 13:09:16 CST