Unable Sign in OBIEE 11g

Error: Unable to sign in in OBIEE 11g
OBIEE 11g has a common issue with it. Some time suddenly OBIEE server stops responding of user authentication.You will confuse if you have not changed any password or changes in repository.

This issue occurs due to an incorrect value for the <DNS> parameter for the BI Server in the Instanceconfig.xml file for the BI Presentation Server compared to the value in the Operating System's ODBC Administration setup for the Oracle BI Server Data Source

Steps to be correct this issue:
There are 3 steps to resolve this issue. If after step1 login fails then go for step 2 and so on.

Steps are:
Step A: Refreshing GUIDs (or Regenerating User GUIDs)

1. Check to see if any error messages regarding GUID mismatch is seen in the sawlog located in \OBI11g\instances\instance3\diagnostics\logs\OracleBIPresentationServicesComponent\coreapplication_obips1 folder/directory.
2. If yes, follow steps to refresh GUID as below:
1. Update the FMW_UPDATE_ROLE_AND_USER_REF_GUIDS parameter in NQSConfig.INI
1. Open NQSConfig.INI for editing at:

2. ORACLE_INSTANCE/config/OracleBIServerComponent/coreapplication_obisn

3. Locate the FMW_UPDATE_ROLE_AND_USER_REF_GUIDS parameter and set it to YES, as follows:
   

   FMW_UPDATE_ROLE_AND_USER_REF_GUIDS = YES;

4. Save and close the file.
2. Update the Catalog element in instanceconfig.xml:
   
   1. Open instanceconfig.xml for editing at:
      

      ORACLE_INSTANCE/config/OracleBIPresentationServicesComponent/
      coreapplication_obipsn

   2. Locate the Catalog element and update it as follows:
      

      <Catalog>
      <UpgradeAndExit>false</UpgradeAndExit>
      <UpdateAccountGUIDs>UpdateAndExit</UpdateAccountGUIDs></Catalog>

   3. Save and close the file.
3. Restart the Oracle Business Intelligence system components using opmnctl:
   

   cd ORACLE_HOME/admin/instancen/bin
   ./opmnctl stopall
   ./opmnctl startall

4. Set the FMW_UPDATE_ROLE_AND_USER_REF_GUIDS parameter in NQSConfig.INI back to NO.
   Important: You must perform this step to ensure that your system is secure.
5. Update the Catalog element in instanceconfig.xml to remove the UpdateAccount GUIDs entry.
6. Restart the Oracle Business Intelligence system components again using opmnctl:
   

   cd ORACLE_HOME/admin/instancen/bin
   ./opmnctl stopall
   ./opmnctl startall

7. After completing step 2, login to OBIEE as the problematic user to verify if you still encounter any login errors.

Step B: Delete user from Repository (RPD) file,  if present

1. Launch admin tool and open RPD in OFFLINE Mode.
2. Click Manage -> Identity -> Users tab to verify if you see this user present
   Note : Normally you will only see list of users when you open RPD in ONLINE mode. Unless the users were created manually in RPD, no users should be visible in OFFLINE mode.
3. If the user is present, delete this user entry from RPD.
4. Save RPD and deploy this changed RPD using EM.
5. Restart OBI Server component.
6. Re-login as the problematic user to see if you still encounter log in error.

If login errors persist after completing Step A and Step B above, then complete the following.
Step C: Delete the cacheduserinfo files from webcatalog

1. Take a backup of your webcatalog.
2. Navigate to \OBIEE11G\instances\instance2\bifoundation\OracleBIPresentationServicesComponent\coreapplication_obips1\catalog\SampleApp\root\users\Administrator\_prefs
3. Delete the files named "cacheduserinfo" and "cacheduserinfo.atr."
4. Open web browser and retest OBIEE 11g login for that user.

Note : The cacheduserinfo and cacheduserinfo.atr files get automatically recreated when the user logs in next time