Hi,
1) Change your ISA sender/receiver if their different between test and production.
I'm not sure what Gentran product you have or if they are all the same, but here where we set it for Gentran 5.21 for Unix:
2) In TP maintenance, open TP transation set (ex 850), goto outbound tab, click on ISA EDIT button. Set ISA15 test/production indicator to either 'T' OR 'P'.
3) Translate your document and check ISA header on output.
That's it.
LEE