An invokable TP is a TP that can be invoked by another TP. Invokable TPs are written or configured through registry or environment variables to supply their names to SNA Server as a notification that they are available for incoming requests. SNA Server invokable TPs can be run on any SNA server or client running Windows NT, Windows 95, Windows version 3.x, or OS/2.
There are two types of invokable TPs:
The recommended method for setting registry or environment variables for autostarted invokable TPs is to use the sample TP configuration program, TPSETUP, or similar code written into your own installation program. For more information about registry or environment variables for invokable TPs, see Configuring Invokable TPs. For information about TPSETUP, see Sample CPI-C TPs in the SDK.
If no local LU alias is registered with autostarted TPs, the resulting SNA Server configuration can be more flexible in responding to invoking requests. For more information about such flexible configurations, see TP Name Not Unique; Local LU Alias Unspecified.
After an autostarted invokable TP is started by SNA Server, the TP issues Accept_Conversation just as an operator-started TP does. Accept_Conversation must provide the TP name that was registered for the TP.
Autostarted TPs must be configured through registry or environment variables to be either queued or nonqueued. All operator-started TPs act as queued TPs.
Note For the Windows NT system, only one copy of a service can be running at any given time; this means that all autostarted TPs that run as services under Windows NT must be queued. To write an autostarted TP so it will run under Windows NT as a service and also run in a nonqueued way, write a multithreaded program with an Accept_Conversation always outstanding.