oim 11.1.2.2.0 starting weblogic error due to ojdbc6.jar error oracle.security.am.admin.config.ConfigurationException: java.lang.ClassNotFoundException: weblogic.jdbc.wrapper.PoolConnection

 oracle.security.am.admin.config.ConfigurationException: java.lang.ClassNotFoundException: weblogic.jdbc.wrapper.PoolConnection

 <Error> <Deployer> <BEA-149205> <Failed to initialize the application 'em' due to error java.lang.ClassNotFoundException: weblogic.jdbc.wrapper.PoolConnection.
java.lang.ClassNotFoundException: weblogic.jdbc.wrapper.PoolConnection

Caused By: java.lang.ClassNotFoundException: weblogic.jdbc.wrapper.PoolConnection

Reason:
above all these error are due to corrupt ojdbc6.jar is present in JAVA_HOME like: /usr/java/jre/lib/ext/, the JDBC driver will be picked from this location, even if the driver is added to the very beginning of the classpath. In this case, a corrupt ojdbc6.jar file was copied to /usr/java/jre/lib/ext/ojdbc6.jar and this caused the problem. if you already have ojdbc6.jar file in java make sure it is compatible with your database version.
you can check database version once u login to sqlplus

Solution:

1. Remove ojdbc6.jar from this location /urs/java/jre/lib/ext/ or replace it with a valid file.
2. Restart the admin and managed server.
3. Retest the issue.