In BW6.7, while testing JDBC connection getting error : java.sql.SQLException: [tibcosoftwareinc][Oracle JDBC Driver] null

Question

In BW6.7, while testing JDBC connection I am getting below error. This error is intermittent and earlier it was working fine. Can you please help me with this issue ?

java.sql.SQLException: [tibcosoftwareinc][Oracle JDBC Driver] null

I have place ojdbc8.jar at

<<TIBCO_HOME>>\bw\6.7\config\drivers\shells\jdbc.oracle.runtime\runtime\plugins\com.tibco.bw.jdbc.datasourcefactory.oracle\lib

and

<<TIBCO_HOME>>\bw\6.7\config\design\thirdparty

also installed oracle-driver