gtpn1m0jNon-SNA Data Communications Reference

Description

The purpose of the CCP is to provide an access method where by the application programs are relatively independent of the communications hardware operation.

Polling and Circuit Assurance

The CCP handles all polling (telling the Terminal Interchange (TI) to send in any messages it has in its buffer) on a time basis. Further, if the amount of available main storage is low, polling is postponed until enough main storage is again available. The CCP also handles the circuit assurance on all communications lines. This is to ensure that the lines are in an operable condition.

Execution of I/O Operations

The CCP executes all communication I/O operations for the application programs. The CCP sets up the CCWs, starts the I/O and handles the interrupts from the operation.

Main Storage Allocation For The Associated I/O Operations

The CCP obtains main storage on input operations and releases the output block.

Character Code Translation For Both Input And Output

The CCP translates all input messages except 3270 Local into an appropriate internal character code. On output, it translates the internal code to the appropriate line code for transmission except for 3270 Local. Both input and output for the 3270 Local are in EBCDIC, except for control characters, which are in hexadecimal.

Input Message Editing And Activation of the Application

This includes the assembly of HS input messages into a single main storage block, if needed, and checking for invalid characters.

CCP performs backspace editing, if required, and then activates the Router. The Router will activate the appropriate application program which will route the message to the proper application segment for processing.

Hardware Error Detection And Correction

The CCP performs all hardware error detection at interrupt time and attempts correction of the error condition. If error correction fails, notification is sent to operations and the line turned down.

Software Error Detection And Processing

The CCP detects all software errors associated with the communications lines and processes them by issuing an appropriate system error.

Communication Considerations for Loosely Coupled Support

The loosely coupled feature allows multiple processors running the same applications to concurrently access a common database. The balancing of the processing load across all processors in a complex is achieved by distributing the input message traffic across the complex. It is irrelevant which processor handles a terminal user's input, since each processor in a complex provides identical service. To a terminal user, say, a reservation agent, a loosely coupled complex has the appearance of a single TPF system. To the system operator, however, the system has the appearance of separate but connected processors. The system operators of a loosely coupled complex has the ability to run the complex from any or all loosely coupled processors.

There are three (3) considerations relative to communications support for the loosely coupled feature.

Component Programs

Packages Used by This Package

The CCP provides the I/O programming required to support four distinct types of communications media:

Consequently, this package consists of four major main storage resident line control programs, and a collection of commonly used main storage resident subroutines. In addition, there are a vast number of file-resident support programs, each of which is associated with one or more of the above line control programs.

1052 or 3215 Console (Control Program Only)

This program performs all the major functions for the 1052 or 3215 and is composed of the following parts:

Of additional interest, the communications multiple used routines of the CCPNUC contains the macros (CRAS and SEND) which interface with the long message transmitter program and which output messages to the 1052/3215 I/O program.

Synchronous Link Lines (Control Program Only)

This program performs most of the major functions listed above (see "FUNCTIONS") for the Synchronous Link lines and is composed of the following parts:

BSC Lines (Control Program Only)

3270 Local Lines (Control Program Only)

E-Type Programs Logically Continuous To The Control Program Resident Programs

Synchronous Link Lines (SLC), Binary Synchronous Communication (BSC), 1052/2315 Console, 3270 Local (LC) I/O Programs, and 3270 Native Console Support (NSC).

E-Type Support Programs (1052/3215 Line Control)

The following file-resident support program is associated with the 1052 line control program.

Support Programs (Synchronous Link Lines)

The following file resident support programs are associated with the Synchronous Link lines:

Support Programs (BSC Lines)

The following file resident support programs are associated with BSC lines:

Support Programs (3270 Local Lines)

Support

The following file-resident support programs are associated with two or more line control programs.