Apart from a new 11.2 scalability option, things like adaptive cursor sharing and cardinality feedback, and anomalies caused by bugs, a new child cursor is generated when a session tries to use a statement that is in the library cache and finds that every child cursors for that statement already in the cache has a different optimizer environment from the session's optimizer environment. It is possible that different optimizer environments will, however, still produce the same execution plan. A common example of changing the optimizer environment is to enable SQL_trace; other options include local changes to workarea_size_policy, sort_area_size, db_file_multiblock_read_count, and so on. If you check v$sql.optimizer_env_hash_value for the statements you may find that they differ. Regards Jonathan Lewis http://jonathanlewis.wordpress.com Oracle Core (Apress 2011) http://www.apress.com/9781430239543 ----- Original Message ----- From: "Sreejith S Nair" <Sreejith.Sreekantan@xxxxxxxxxx> To: <oracle-l@xxxxxxxxxxxxx> Sent: Thursday, February 02, 2012 1:36 PM Subject: Child Cursor and Plan Hi Friends, Oracle 11.2.0.2 on Solaris 10. From my understanding a child cursor is generated when a sql statement will have multiple execution plans. Here is what I see in one of our database SYS> select sql_id,child_number,hash_value,PLAN_HASH_VALUE,CHILD_ADDRESS from v$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 -- 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@xxxxxxxxxx 8 www.ibsplc.com DISCLAIMER: "The information in this e-mail and any attachment is intended only for the person to whom it is addressed and may contain confidential and/or privileged material. If you have received this e-mail in error, kindly contact the sender and destroy all copies of the original communication. IBS makes no warranty, express or implied, nor guarantees the accuracy, adequacy or completeness of the information contained in this email or any attachment and is not liable for any errors, defects, omissions, viruses or for resultant loss or damage, if any, direct or indirect." -- //www.freelists.org/webpage/oracle-l ----- No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1913 / Virus Database: 2112/4780 - Release Date: 02/01/12 -- //www.freelists.org/webpage/oracle-l