Re: control file i/o buffer allocations
Date: Sat, 22 Feb 2020 20:15:41 +0000
Message-ID: <LNXP265MB15624626206BFF5D0E6ABC5EA5EE0_at_LNXP265MB1562.GBRP265.PROD.OUTLOOK.COM>
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/
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Received on Sat Feb 22 2020 - 21:15:41 CET