What Is a Transaction Program?

A transaction program is a block of code, or part of an application program, that uses APPC communications functions. Application programs use these functions to communicate with application programs on other systems that support APPC. A transaction program has a 64-byte name (tp_name).

Your transaction program can obtain LU 6.2 services through either of the following APIs:
  • APPC—Advanced Program-to-Program Communication allows transaction programs to exchange information across an IBM® SNA network using the syntax and verbs defined by IBM® for using an LU 6.2 session.
  • CPI-C—Common Programming Interface for Communications (CPI-C) allows transaction programs to exchange information across an IBM® SNA network using the syntax, defined by IBM® in the Common Programming Interface component of the SAA®, for using an LU 6.2 session. Because this API is implemented for many platforms, CPI-C applications can be easily ported.

Transaction programs issue APPC verbs to invoke APPC functions. See Implementing APPC Transaction Programs, for details about how transaction programs issue APPC verbs. Transaction programs can issue CPI Communications calls to invoke CPI Communications functions. The CPI Communications calls let application programs take advantage of the consistency that SAA® provides. See CPI Communications Transaction Programs for information about the CPI Communications calls.

Programs do not need to be written to the same LU 6.2 API in order to communicate with each other. In particular, a transaction program written to the APPC API can communicate with a transaction program written to CPI-C.