We "Service Code" as a short name for an application, eg "GolfLine" might be the short name we refer to application C:\MyApps\GolfRegistration.TAP. Setting @SERVICE_CODE is not required to use the RunTAP step.
Check step number 146 in DNIS_RouteToService.TAM. It is an SQL Statement step to lookup the TAP file in the theoretical table "DNISLookup". In one of our "Service Branching" applications we have more than 30 TAPs that could be called, so its easier for us to reference them by a short name.
If you don't have an entry in the Help file for RunTAP, then you have an older version of TeleFlow. You can upgrade it here:
http://www.engenic.com/downloads
If you just want an up-to-date Help file, download it from either of these links:
TeleFlow.chm
TeleFlow.pdf
The new Help may reference functionality that you don't have in your current TeleFlow, but the RunTAP step documentation should be accurate.