Parameter DEFAULT_VALUE changed in table fnd_request_set_program_args non taking account when execut

Hello,

For some requests, after changing the parameter DEFAULT_VALUE in table fnd_request_set_program_args, the DEFAULT_VALUE is successfully corrected.
Moreover the changed value is correct in EBS Forms.
But afterwards the executed request aborts because it's still launched with the old DEFAULT_VALUE.
Of course this issue may be corrected manually in EBS but i want to do this change by a script.
I suppose modifying the table fnd_request_set_program_args is not sufficient. What are the other tables to update?
Or, better, is there a specific API for this change?

Regards,
Armel