How do I achieve a webSphereDefaultIsolationLevel of  "Read Uncommited" in WAS 7.0.0.31.

I change the datasource custom property value to 1 , which corresponds to Read Uncommitted , restarted my nodeagents,  JVMs, n my connection to DB looks good

When the transaction is being validated I get the following  error 

Could not open JDBC Connection for transaction; nested exception is java.sql.SQLException: READ_COMMITTED and SERIALIZABLE are the only valid transaction levelsDSRA0010E: SQL State = 99999, Error Code = 17,030

I am using Oracle as a backend database with ojbc6.jar at a version 11.2.0.3.