DATA COMMUNICATIONS

The UN IVAC

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Operating System is designed to interface with programs having online requirements. A flexible communications control program .combined with an efficient scheduling and interrupt processing supervisor provide the environment for online processing. The general message flow for communications processing is shown in Figure

6-8.

As stated in Section 2, communications capability is provided by means of a Data Communications Subsystem (DCS) connected to the multiplexer channel or the communication Intelligence Channel (CIC). Similar facilities are provided for both system configurations.

The communication control program consists of the following functional components:

• Physical I/O control system (IOCS) .. Me,ssage control program

• Message processing programs

These components are described in the following paragraphs.

6.5.1. Physical I/O Control System

The physical 10CS is a main storage resident extension of the supervisor and requires main storage to operate in the same processing state as the supervisor. Its primary function is to control the communcations environment of the operating system. It includes I/O dispatcher and interrupt handling routines.

6.5.2. Message Control Program

The message control program, which interfaces with the resident physical IOCS, is the major component of the communications control program. It operates as a separate job with prime priority on the supervisor switch list.

The responsibilities of the message control program include initiating and controlling:

•

Message flow

•

Line control

•

Message acknowledgment

•

^Buffering

•

Main and direct access storage queuing

•

Error handling

•

Message translation

•

Polling sequences

•

Operator-console communications

co (.11

Options enable users to audit error conditions, maintain error counts and header summaries, and provide traffic analysis information. Options are also provided to support audit trails, data integrity, and the various editing functions required in a communications environment. Support is provided for multiple destination routing, broadcast messages, rerouting, automatic store and forward of messages and message switching.

Users are permitted to examine messages after they have been received and before they are transmitted in order to perform special data conversion and editing (subject to systems considerations).

Queuing is supported on disc storage devices and main storage. Messages are queued on a priority basis by destination. Urgent messages are recognized as they are received and temporarily override other message priorities during transmission.

Message queue overflow from main storage to direct access storage is supported at the option of the user.

Support is provided for automatic polling, dial-out, automatic answering, and manual dialing.

The following terminals are supported:

• TE LETYPE Models 28, 32, 33, 35, and 37.

• UN ISCOPE 100 Display Terminal

• UN IVAC DCT 500, 1000, and 2000 Data Communications Terminals

• UN IVAC 9200/9300/9400 Systems

• UNIVAC 1004/1005 Subsystems

• IBM 2780 binary synchronous communications

The system handler interface has been standardized, facilitating the subsequent incorporation of new communications device handlers into the system. The above list does not preclude the addition of such device handlers as may be required.

6.5.3. Message ProcessJng Program

The message processing program is user-generated coding which processes incoming messages and generates any applicable response messages. This program interfaces with the message control program through macro instructions provided for this purpose.

Macro instructions are provided to direct the message control program to control:

• Sending and receiving of messages Routing

Message switching Time and data stamping

Sequencing and sequence checking Source I.D. validation

• Message queue maintenance

• Destination validation

In addition, two macro instructions are provided to control:

• Length checking

• Priority control

6.5.4. Remote Job Entry

Communications input readers and output writers provide spoolin and spool out of remote entry jobs independent of other system functions. The same communications networks which are used for such applications as inventory updating or inquiry and transaction processing may be alternately used to enter remote jobs into the system. Priority queues exist within the operating system for scheduling jobs. Job and system status are available for operator inquiry.

The remote job control language is identical to the standard onsite job control language with the exception that some additional information which uniquely identifies the remote station is required. An option is provided which allows outputs of remotely executed jobs to be delivered to central site peripherals rather than returned to the remote station.

6.5.5. Network Definition

Macro instructions are provided to define the system line groups and terminals. Common line sharing is permitted to provide diagnostics with the capability to test a given remote device while other devices are active. Dynamic reconfiguration of destination terminals is provided to allow user flexibility when a particular terminal is down or a particular communications environment requires a viable line terminal configuration.

6.5.6. User Own Code

Programs are permitted to use own code to perform special data conversion and editing on all messages entering and leaving the system.

6.5.7. Error Checking and Message Recovery

The communications control program provides automatic error recovery and message recovery, as needed. It provides for the interception, cancellation, and logging of messages in error.

Message retrieval and checkpoint/restart of message files can be requested on a message or file.

6.5.8. Multiple Message Processing Programs

A mUltiple number of message processing programs is permitted to operate concurrently under OS/7 subject to availability of system resources.

ProgramtOriented networks operating under the control of a message processing program are able to create files of information to be processed on another network by another message processing program, concurrently, if desired.

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