Home -> Mailing Lists -> Oracle-L -> RE: control file i/o buffer allocations

RE: control file i/o buffer allocations

From: Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Date: Mon, 24 Feb 2020 06:28:47 +0000
Message-ID: <16682_1582525736_5E536D28_16682_14007_1_c7dd4bc24ecc4b6ea38d8bcb19ea486d_at_vontobel.com> 






Thanks, Jonathan.



Last week the MOS search on SQL_ID frccccnh76gtx didn't return anything, now it does.



Best regards,



Nenad



https://nenadnoveljic.com/blog/




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




From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk> 
Sent: Samstag, 22. Februar 2020 21:16


To: ORACLE-L (oracle-l_at_freelists.org) <oracle-l_at_freelists.org>; Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Subject: Re: control file i/o buffer allocations




Known bug:



30098251 : WNNN PROCCESSES CREATE AN EXCESSIVE NUMBER OF OPEN CURSOR


Fixed in 20.1



There are a number of patches to older versions.



Regards


Jonathan Lewis





From: oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on behalf of Noveljic Nenad <nenad.noveljic_at_vontobel.com>
Sent: 21 February 2020 15:37


To: ORACLE-L (oracle-l_at_freelists.org)
Subject: control file i/o buffer allocations



I've been observing unusually large process memory allocations for space manager slaves on 18c, for example:



SQL>



select program,module,action,event from v$session where sid = 712  ;



PROGRAM                                          MODULE                                                           ACTION                                                           EVENT


------------------------------------------------ ---------------------------------------------------------------- ---------------------------------------------------------------- ----------------------------------------------------------------


oracle_at_SERVER (W007)                           KTSJ                                                             KTSJ Slave                                                       Space Manager: slave idle wait





As we can see below, a single space manager process has allocated ~144MB for 'control file i/o buffer':



select category,name,heap_name,bytes,allocation_count
from v$process_memory_detail where name='control file i/o buffer' ;



CATEGORY        NAME                       HEAP_NAME            BYTES ALLOCATION_COUNT


--------------- -------------------------- --------------- ---------- ----------------


SQL             control file i/o buffer    kxs-heap-w       144775944              459





Further, it had 459 allocations which roughly matches the number of open cursors on v$datafile query that aren't getting closed:



select sql_id,sql_text,cursor_type,count(*) from v$open_cursor
  where sid = 712 group by sql_id,sql_text,cursor_type order by count(*) desc ;



SQL_ID        SQL_TEXT                                                     CURSOR_TYPE                                                        COUNT(*)


------------- ------------------------------------------------------------ ---------------------------------------------------------------- ----------


frccccnh76gtx select rfile# from v$datafile where file# = :1               OPEN-RECURSIVE                                                          461
2360z2hxanh3w select nvl(con_id, 0), lobtsn, lobrdba, lobobjid from x$lobs SESSION CURSOR CACHED                                                     1





Any ideas on what might have caused this allocation? Is it really related to open cursors? Why aren't the cursors getting closed? How to release the memory back without restarting these processes? How to prevent this from happening? How to reproduce it at will?



Thanks in advance,



Nenad



https://nenadnoveljic.com/blog/






Please consider the environment before printing this e-mail.
Bitte denken Sie an die Umwelt, bevor Sie dieses E-Mail drucken.



Important Notice



This message is intended only for the individual named. It may contain confidential or privileged information. If you are not the named addressee you should in particular not disseminate, distribute, modify or copy this e-mail. Please notify the sender immediately by e-mail, if you have received this message by mistake and delete it from your system.
Without prejudice to any contractual agreements between you and us which shall prevail in any case, we take it as your authorization to correspond with you by e-mail if you send us messages by e-mail. However, we reserve the right not to execute orders and instructions transmitted by e-mail at any time and without further explanation.
E-mail transmission may not be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete. Also processing of incoming e-mails cannot be guaranteed. All liability of Vontobel Holding Ltd. and any of its affiliates (hereinafter collectively referred to as "Vontobel Group") for any damages resulting from e-mail use is excluded. You are advised that urgent and time sensitive messages should not be sent by e-mail and if verification is required please request a printed version.
Please note that all e-mail communications to and from the Vontobel Group are subject to electronic storage and review by Vontobel Group. Unless stated to the contrary and without prejudice to any contractual agreements between you and Vontobel Group which shall prevail in any case, e-mail-communication is for informational purposes only and is not intended as an offer or solicitation for the purchase or sale of any financial instrument or as an official confirmation of any transaction.
The legal basis for the processing of your personal data is the legitimate interest to develop a commercial relationship with you, as well as your consent to forward you commercial communications. You can exercise, at any time and under the terms established under current regulation, your rights. If you prefer not to receive any further communications, please contact your client relationship manager if you are a client of Vontobel Group or notify the sender. Please note for an exact reference to the affected group entity the corporate e-mail signature. For further information about data privacy at Vontobel Group please consult www.vontobel.com<https://www.vontobel.com>.



Important Notice
 


 This message is intended only for the individual named. It may contain confidential or privileged information. If you are not the named addressee you should in particular not disseminate, distribute, modify or copy this e-mail. Please notify the sender immediately by e-mail, if you have received this message by mistake and delete it from your system.
 Without prejudice to any contractual agreements between you and us which shall prevail in any case, we take it as your authorization to correspond with you by e-mail if you send us messages by e-mail. However, we reserve the right not to execute orders and instructions transmitted by e-mail at any time and without further explanation.
 E-mail transmission may not be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete. Also processing of incoming e-mails cannot be guaranteed. All liability of Vontobel Holding Ltd. and any of its affiliates (hereinafter collectively referred to as "Vontobel Group") for any damages resulting from e-mail use is excluded. You are advised that urgent and time sensitive messages should not be sent by e-mail and if verification is required please request a printed version.
 Please note that all e-mail communications to and from the Vontobel Group are subject to electronic storage and review by Vontobel Group. Unless stated to the contrary and without prejudice to any contractual agreements between you and Vontobel Group which shall prevail in any case, e-mail-communication is for informational purposes only and is not intended as an offer or solicitation for the purchase or sale of any financial instrument or as an official confirmation of any transaction.
 The legal basis for the processing of your personal data is the legitimate interest to develop a commercial relationship with you, as well as your consent to forward you commercial communications. You can exercise, at any time and under the terms established under current regulation, your rights. If you prefer not to receive any further communications, please contact your client relationship manager if you are a client of Vontobel Group or notify the sender.
 Please note for an exact reference to the affected group entity the corporate e-mail signature.
 For further information about data privacy at Vontobel Group please consult www.vontobel.com.



--



http://www.freelists.org/webpage/oracle-l
Received on Mon Feb 24 2020 - 07:28:47 CET












Original text of this message