gtps2m3iACF/SNA Data Communications Reference

Input Message Router Exit

Specifying COMEXIT=YES on the SIP MSGRT macro provides the user exit routine (segment COBC) to be included in the generated TPF system. The sample code released with TPF consists of nothing more than a 'BACKC' macro. The user should replace this with the desired logic.

This routine is given control whenever a message is received by the Message Router or the Communication Source package and the destination is an application. The message includes both those from terminals and those generated by another application.

It should be noted that upon return from this routine, TPF no longer examines the input message and all subsequent processing is based entirely upon the RCPL information. If the destination specified in the RCPL has been changed by this routine to anything other than a local TPF application, TPF issues a 'ROUTC' upon receiving control from this routine.

The INPUT/OUTPUT interface between the TPF packages (Message Router and Communication Source) and the user coded COBC segment is as follows:

The TPF services and facilities that may be started by the routine are:

The Non-SNA Log Processor.

The Unsolicited Message Package.

The SMP Prefixing Facility.

All TPF macros.

The following are examples of the services that could be implemented in a user's input edit routine.

Data Transformation
The input message text may be modified to a format acceptable to the application. This allows users to attach new terminals to existing applications and non-SNA terminals to new applications.

Data De-compaction and De-compression
Data, encoded for transmission efficiency, is decoded.

Message Verification
An error message may be returned to the message originator and the message discarded.

Prefixing
This special case of transaction analysis allows system operators to denote the application, subsystem or subsystem_user to process the command entered. For example, TPF supports operator command prefixing, where the command is prefixed with the application, subsystem or subsystem_user name followed by the character /. For many users this format is unacceptable and operationally awkward. Therefore, for those users that wish to use an alternate prefixing technique, the input edit routine may translate an installation defined prefix to the prefix format required by TPF.

Transaction Analysis
The input text may be analyzed to determine the application to process the input message.

User Written Transaction Routing
Some users may wish to bypass the TPF Log Processor and create their own. For example, assume a network where terminal users frequently access multiple TPF applications and the TPF requirement for a terminal user to logon is too costly in terms of operator efficiency. Here the input edit routine could be used to implicitly logon the terminal based on the input message text. The character $ may be used to signify an implicit logon and the character immediately following the $ signifies the application. Further assume that the presence of text following $aaaa determines whether the connection is just for this message or all following input. Then, in a network where terminal users frequently require access to multiple applications, the terminal user could simply prefix their input rather than logging into the required application.

Unsolicited Message
The user edit routine may request the next unsolicited message queued to the terminal and transform the input into a LOGU request, setting the input destination to the 4 characters, LOGI.

ECB Set Up
The user edit may set or change the following:

Input from the following sources is passed to the user Input Edit routine: