Test Data Manager

When using javlein I am getting ORA-12154 TNS:could not resolve the connect identifier specified. I can connect to the databases with TD Data Maker without issues. I am attempting to perform a sub-set bulk copy.

I have noticed this TNS issue also happens in Oracle Activity as well.But in Oracle Activity, we can work around by setting the Connection String property with the TNS String Eg:
Data Source= (DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=myhost)(PORT=1234)))(CONNECT_DATA=(SERVICE_NAME=MYDB)));User Id=uname;Password=password

But in Bulk Copy, we can do this WA for the Reader but for writer there is no option to put connection string. 

ORA-12154 usually means "service name" (global database name) or "sid" (one of them has to be specified) is incorrect. Users tend to confuse these two.