OID 11g-- Analysis , http-500 internal server error in ODSM, http://hostname:port/odsm

In one of our customer 's OID environment which was integrated to EBS and SSO, the clients were encountering HTTP-500 Internal Server Error while trying to reach Oracle Directory Services Manager(ODSM) url..

The problematic url was used for managing the OID configuration , like checking the attributes etc.
The error was reported as follows;

OID system is working properly , but we cant open its management interface to control the configuration or its attributes.. In the past, when we see the error, we were just refreshing the web page and were able to continue our work, but nowadays refreshing the webpage does not fix the problem anymore..
Also, when we restart the OID services, the problem dissapears for a while.. On the otherhand, this is not an applicable solution for us.. In Oracle Support, it is said that the error may be related wit Browser Certifications, but in our case it is not relevant.

Okay..  

When I check Oracle Support , I saw that one of the workaround was restarting the managed server ..

Case 3 in the document "CheckList For OID 11g ODSM Page Launching / Loading / Displaying 

Problems Or Errors (Doc ID 972416.1)" was mentioning the restart as a workaround..

But this workaround could not be applied as a solution in this case, because the error was encountring periodically and repeatedly.

So , I requested the OID 's Managed Server log for analysis.

The managed server name was wls_ods1 ,which was a default one ...

After setting the domain environment; the log file could be reached by the following directory path;

$MW_HOME/user_projects/domains/domain_name/servers/server_name/logs

Analyzing the log file of a Weblogic server is like debugging a java program to me.

I have basically, searched for the word Exception that led me to the following..

<[ServletContext@1709139423[app:odsm module:/odsm path:/odsm spec-version:2.5 version:11.1.1.2.0]] Servlet failed with Exception
java.lang.RuntimeException: java.lang.Exception: MDSLockedSessionManager already registered. Can't register more than one.
.....
.....
Caused By: java.lang.Exception: MDSLockedSessionManager already registered. Can't register more than one.
at oracle.adf.share.mds.MDSTransManager.registerMDSLockedSessionManagerInst(MDSTransManager.java:132)
at oracle.adf.share.mds.MDSTransManager.registerMDSLockedSessionManager(MDSTransManager.java:124)

So it was obvious that the Exception "java.lang.RuntimeException: java.lang.Exception: MDSLockedSessionManager already registered. Can't register more than one"  was the cause that I was looking for.. Because the error was saying that Servlet was failed , and the path was the reflecting the odsm.

After finding the low level cause of the problem, I jumped in to the Oracle Support, and found the following document : Accessing ODSM 11g 11.1.1.7 Intermittently Fails with: java.lang.Exception: MDSLockedSessionManager already registered. Can't register more than one. (Doc ID 1586149.1)

Finally, this document brought me to the following bug : bug 17997221

To get the patch for this bug , the customer needed to open an SR to the Oracle Support.

It is planned that; once obtained, the patch was going be applied to the ORACLE_COMMON home of OID .. 

This Oracle home was hosting the binary,library and JRF files which are used for controlling the Fusion..

I will write the conclusion of this story when the patch will be applied, but I m sure that this action plan will fix the problem.