RE: Child Cursor and Plan

There are many reasons why a child cursor is created. It could be that the optimizer environment differs or because the bind variablen had a different length, ... . But, this does not have to mean that a different sql plan will be used.

You can check the reasons why a certain child exists for a cursor in the v$sql_shared_cursor view.

Regards,  

Freek D'Hooge
Uptime
Oracle Database Administrator
email: freek.dhooge_at_uptime.be
tel +32(0)3 451 23 82
http://www.uptime.be
disclaimer: www.uptime.be/disclaimer

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Sreejith S Nair Sent: donderdag 2 februari 2012 14:37
To: oracle-l_at_freelists.org
Subject: Child Cursor and Plan

Hi Friends,
Oracle 11.2.0.2 on Solaris 10.

From my understanding a child cursor is generated when a sql statement will have multiple execution plans. Here is what I see in one of our database

SYS> select sql_id,child_number,hash_value,PLAN_HASH_VALUE,CHILD_ADDRESS from v$sql where sql_id='c8gnrhxma4tas';

SQL_ID CHILD_NUMBER HASH_VALUE PLAN_HASH_VALUE CHILD_ADDRESS
------------- ------------ ---------- --------------- ----------------

c8gnrhxma4tas            0 1721918808      4024720576 00000004481E01A8
c8gnrhxma4tas            1 1721918808      4024720576 0000000456DEF070
c8gnrhxma4tas            2 1721918808      4024720576 0000000448F3C210
c8gnrhxma4tas            3 1721918808      4024720576 000000047CA5BD30
c8gnrhxma4tas            4 1721918808      4024720576 0000000448476B88
c8gnrhxma4tas            5 1721918808      4024720576 000000047C217998
c8gnrhxma4tas            6 1721918808      4024720576 00000004483B0B78
c8gnrhxma4tas            7 1721918808      4024720576 000000047C3F9668

Here I see that CHILD_NUMBER and different CHILD_ADDRESS are generated for same PLAN_HASH_VALUE. Can someone please give some light on what exactly is a child cursor ?
This is what I got from Google. Could not find a proper definition in documentation.May be I missed ?

The parent cursor contains the SQL statement text only, but no execution plan.
Execution plans are found in child cursors. Child cursors are also called versions.

With Regards,
Sreejith  

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Sreejith S Nair
Associate Systems Architect | AOS DBA Team IBS Software Services Private Ltd.
2nd Floor, IBS Campus, Technopark Campus, Trivandrum - 695 581, Kerala, India
((Direct) +91 471 661 4707 ) +91 808 648 5523 *sreejith.sreekantan_at_ibsplc.com
8 www.ibsplc.com

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http://www.freelists.org/webpage/oracle-l Received on Thu Feb 02 2012 - 07:56:25 CST