|
Problem IT14894
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Status: Closed |
HIGH CONTENTION ON 'SESSION' MUTEX WHEN LOTS OF SESSIONS SELECT DATA FROM SYSMASTER:SYSSESSIONS
|
| product: |
INFORMIX SERVER / 5725A3900 / C10 - IDS 12.10 |
| Problem description: |
If you have lots of user threads connecting to the database and
running select statements from sysmaster:syssessions, you may
see a high contention on the 'session' mutex. User threads are
waiting for 'mutex wait session'. All new connections are slow
connecting to the database.
This problem happens on IDS12.10.FC4 onward. The same problem
does not happen on IDS 12.10.FC3 and IDS 11.70.FC8.
Example : When there is the following SQL statement to get
session id for the new connection.
select UNIQUE sid FROM sysmaster:syssessions
where pid = ? AND username = ?;
When the number of connections reaches 2000 - 3000, you will see
'session' mutex from onstat -g ath, and onstat -g lmx.
onstat -g lmx
IBM Informix Dynamic Server Version 12.10.FC6 -- On-Line -- Up
00:10:16 -- 709888 Kbytes
Locked mutexes:
mid addr name holder lkcnt
waiter waittime
19 4407b838 session 5111 0
5237 0
5234 0
4119 0
4105 0
onstat -g ath
...
5308 50436658 4ea1cea8 1 mutex wait
session 1cpu sqlexec
5318 4c1d4958 4ea1bd28 1 mutex wait
session 1cpu sqlexec
5322 4dd34028 4ea0d9a8 1 mutex wait
session 1cpu sqlexec
5328 4c6c7b50 4ea1aba8 1 mutex wait
session 1cpu sqlexec
5329 4bdba178 4ea188a8 1 mutex wait
session 8cpu sqlexec
5331 4f2e9608 4ea12868 1 mutex wait
session 1cpu sqlexec
5341 4e848028 4ea17728 1 mutex wait
session 1cpu sqlexec
5342 4cd93568 4ea1c5e8 1 mutex wait
session 8cpu sqlexec
... |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* Users who frequently query sysmaster:syssessions or the *
* similar session-related pseudo tables. *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Update to IBM Informix Server 12.10.xC8 *
**************************************************************** |
| Local Fix: |
Workaround : Select session id using dbinfo("session id") |
| Solution |
|
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 21.04.2016
09.12.2016
09.12.2016 |
| Problem solved at the following versions (IBM BugInfos) |
12.10.xC8
|
| Problem solved according to the fixlist(s) of the following version(s) |
