|
Problem IT16670
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Status: Closed |
HIGH CONTENTION ON 'SESSION' MUTEX WHEN LOTS OF SESSIONS SELECT DATA FROM SYSMASTER:SYSSESSIONS
|
| product: |
INFORMIX SERVER / 5725A3900 / B70 - IDS 11.70 |
| Problem description: |
If you have lots of user threads connect to database and run
selecting data from sysmaster:syssessions, you may see a high
contention on 'session' mutex. User threads are waiting for
'mutex wait session'. All new connections are getting slow to
connect to database.
This problem happens on IDS12.10.FC4 onward. The same problem
does not happen on IDS12.10.FC3, IDS11.70.FC8
Example : When there is a 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 reach 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 11.70.xC9 *
**************************************************************** |
| 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 :
| 18.08.2016
09.06.2017
09.06.2017 |
| Problem solved at the following versions (IBM BugInfos) |
11.70.xC9
|
| Problem solved according to the fixlist(s) of the following version(s) |
