I believe with config.dat parms that they are not explicitly specified if using the default value. You only add them to config.dat if you want to override the default. So adding the parm to config.dat with your required parm should have the desired effect.
Anyway what I was looking for a way to double check the value of this parameter through a command.
running "ctmipc –dest NS –MSGID DNS –data “CTM_DNS_RESOLVE_EXPIRE x”"can update temporary the value and it would not be reflected on config.dat file