You need to choose which dynamic network drivers to use at your site. Your choice depends on the protocols installed at your site and the types of processing you want to achieve.
Use this topic overview to understand issues involved in selecting your drivers:
SAA is an architecture composed of a set of selected software interfaces, conventions, and protocols designed to provide a framework for developing distributed applications. The key benefits of SAA are portability, consistency, and connectivity. The components of SAA are specifications for the key application interfaces points:
Common user access
Common communication support
Common Programming Interface (CPI)
The SAA Common Programming Interface specifies the languages and services used to develop applications across SAA environments. The elements of the CPI specification are divided into two parts:
Processing logic
High level language—COBOL, C, Fortran, RPG
Procedure language—REXX
Application generator—Cross Systems Product/Application Development (CSP/AD)
Services
Communication interface or CPI-C—API for writing APPC applications.
Database interface—Structured Query Language (SQL)
Dialog interface—Interactive System Productivity Facility (ISPF)
APPC/MVS is an SNA application that extends APPC support to the MVS operating system. The primary role of APPC/MVS is to provide full LU 6.2 capability to MVS applications to allow communication with other applications in a distributed SNA network.
APPC/MVS provides programming support by providing an API based on the CPI-C interface. This interface is implemented in a lower-level API that is MVS-specific. The CPI-C calls all begin with CM; for example, CMALLC (Allocate). The MVS calls all begin with ATB; for example, Send_data (ATBSEND). The CPI-C calls are portable to non-MVS platforms while the ATB calls are not portable to non-MVS platforms.
SNA is an IBM Network Architecture composed of a set of software interfaces, protocols, and operational sequences for transmitting information through and controlling the configuration and operation of networks.
LU 6.2 refers to the SNA Logical Unit Type 6.2, which supports general communication between programs in a distributed environment. LU 6.2 is characterized by peer-to-peer communications support, comprehensive end-to-end error processing, optimized data transmission flow and a generic API.
The LU 6.2 system is layered functionally. It can be represented by a set of finite-state machines. Each of these machines has a finite number of states and a set of rules that govern the transition from one state to another. These finite state machines govern the behavior of LU 6.2 devices by guaranteeing that a given input always produces the same output.
APPC is peer level data communication support based on the SNA LU 6.2 protocols.
All inbound transactions require a scheduler. Under MVS, the ASCH address space performs this function by scheduling inbound transactions in initiators under its control. The relationship between ASCH and its initiators is very similar to that of JES (Job Entry System), which schedules jobs in initiators under its control.
The Control region is the scheduler running under CICS. The Message Region running under the Control region corresponds to the initiators used by ASCH.
CICS differs from MVS and IMS TM because it does not schedule transactions in a separate address space. It schedules them as a task within its own address space.
Outbound transactions use a file called the Side Information File to map a name to an SNA logical unit. MVS and IMS TM both use this file.
