PQ72570: CLASSCASTEXCEPTIONS SEEN IN MEM TO MEM MODE WITH LOW PERFORMANCEOPTION SELECTED ON THE SESSION MANAGER SERVICE

 A fix is available

5.0.2: WebSphere Application Server Version 5.0 Fix Pack 2 (Version 5.0.2)



APAR status
Closed as program error.

Error description
I am using trade3 benchmark application. I do not know what
attributes the application writes to the session object. But
the sequence is simpler. You do not need to restart a server,
and an error occurs from the start.
1. Install trade3 to a cluster including two servers.
2. In the same way as your mail, enable mem to mem in both
   client and server mode on the both server
3. Set tuning level LOW in custom tuning parameter of
   distributed environment setting.
3. Send several Get requests to 
http://xxx/trade/scenario
4. There is an error statement in SystemOut.log
http://trade/scenario internally calls other servlets (login,
quote, portfolio, logout .. ) randomly according to predefined
probability distribution. So it keeps current states ( user id )
in a session. If it works correctly, it travels several servlets
with the same user id for a while. But if it cannot retrieve a
user id from a session, it starts with a new user id.
When I select Byte serialization, http://trade/scenario always
start with a new user id. No error is displayed in a web page,
but an error statement is output in SystemOut.log
Session affinity is enabled by HTTP server plug-in. So all the
requests are sent to the same application server. I cannot
understand why such an error occurs. But I am sure that the same
application works correctly with Object serialization, DB
persistence, and in-memory session management. Operating system
is RedHat Linux V7.3.
Local fix Problem summary
****************************************************************
* USERS AFFECTED: WebSphere Application Server -- Session      *
*                 Manager Users                                *
****************************************************************
* PROBLEM DESCRIPTION: ClassCastExceptions seen in Mem to      *
*                      Mem Mode with Low Performance option    *
*                      selected on the Session Manager Service *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
The Session Manager has various options which offer different
performance levels.  In the Mem to Mem Mode, if the Low
Performance option was selected, on the second request for the
same HttpSession a ClassCastException was being thrown.
Problem conclusion
This problem has been fixed and the ClassCastExceptions are no
longer thrown by the Session Manager when Low Performance is
enabled.
Temporary fix Comments
APAR information
APAR number PQ72570
Reported component name WAS BASE 5.0
Reported component ID 5630A3600
Reported release 00I
Status CLOSED PER
PE NoPE
HIPER NoHIPER
Special Attention NoSpecatt
Submitted date 2003-03-27
Closed date 2003-04-28
Last modified date 2003-04-28

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Modules/Macros
SESSIONS          

Publications Referenced

Fix information

Applicable component levels
R003 PSY    UP
R00A PSY    UP
R00H PSY    UP
R00I PSY    UP
R00S PSY    UP
R00W PSY    UP


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > General
Operating system(s):
Software version: 00I
Software edition:
Reference #: PQ72570
IBM Group: Software Group
Modified date: Apr 28, 2003