Error while opening JDBC connection.: Unexpected exception while enlisting XAConnection java.sql.SQLException: XA error: XAResource.XAER_RMFAIL start() failed

When we are keeping two Data Sources in Weblogic server and if both the data sources are pointing to one database, we gets this error. 

In order to resolve this issue, keep only one data source for one database so that weblogic server's multithreading system will handle the Database connection pool. If both the datasource points to same database, weblogic server works on parallel system and multiple thread will point to the dame database and connection will not be established due to the existing connection.