Using batch data interchange

The CICS batch data interchange program provides for communication between an application program and a named data set (or destination) that is part of a batch data interchange logical unit in an outboard controller, or with a selected medium on a batch logical unit or an LU type 4 logical unit. This medium indicates the required device such as a printer or console.

The term outboard controller is a generalized reference to a programmable subsystem, such as the IBM® 3770 Data Communication System, the IBM 3790 Data Communication System, or the IBM 8100 System running DPCX, which uses SNA protocols. Details of SNA protocols and the data sets that can be used are given in IBM 3767/3770/6670 Guide. Figure 1 gives an overview of batch data interchange.

This picture gives a diagrammatic overview of a CICS system using batch data interchange to move data to a remote programmable susbystem that controls a card device, a printer, and terminals. — Figure 1. CICS batch data interchange

The following batch data interchange commands are provided:

ISSUE QUERY: Initiate transfer of a data set to the CICS application program.
ISSUE RECEIVE: Read a record from a data set or read data from an input medium.
ISSUE SEND: Transmit data to a named data set or to a selected medium.
ISSUE ADD: Add a record to a data set.
ISSUE REPLACE: Update (replace) a record in a data set.
ISSUE ERASE: Delete a record from a data set.
ISSUE END: Terminate processing of a data set.
ISSUE ABORT: Terminate processing of a data set abnormally.
ISSUE NOTE: Request the next record number in a data set.
ISSUE WAIT: Wait for an operation to be completed.

Where the controller is an LU type 4 logical unit, only the ISSUE ABORT, ISSUE END, ISSUE RECEIVE, ISSUE SEND, and ISSUE WAIT commands can be used.

Where the data set is a DPCX/DXAM data set, only the ISSUE ADD, ISSUE ERASE, and ISSUE REPLACE commands can be used.

Refer to Dealing with exception conditions for information about how to deal with any exception conditions that occur during execution of a batch data interchange command.

Destination selection and identification

All batch data interchange commands except ISSUE RECEIVE include options that specify the destination. This is either a named data set in a batch data interchange logical unit, or a selected medium in a batch logical unit or LU type 4 logical unit.

When you select a destination by named data set, the DESTID and DESTIDLENG options must always be specified, to supply the data set name and its length (up to a maximum of eight characters). For destinations having diskettes, the VOLUME and VOLUMELENG options may be specified, to supply a volume name and its length (up to a maximum of six characters); the volume name identifies the diskette that contains the data set to be used in the operation. If the VOLUME option is not specified for a multidiskette destination, all diskettes are searched until the required data set is found.

As an alternative to naming a data set as the destination, various media can be specified by means of the CONSOLE, PRINT, CARD, or WPMEDIA1–4 options. These media can be specified only in an ISSUE ABORT, ISSUE END, ISSUE SEND, or ISSUE WAIT command.

Definite response (DEFRESP option)

CICS uses terminal control commands to carry out the functions specified in batch data interchange commands. For those commands that cause terminal control output requests to be made, the DEFRESP option can be specified. This option has the same effect as the DEFRESP option of the SEND terminal control command; that is, to request a definite response from the outboard controller, irrespective of the specification of message integrity for the CICS task (by the system programmer). The DEFRESP option can be specified for the ISSUE ADD, ISSUE ERASE, ISSUE REPLACE, and ISSUE SEND commands.

Waiting for function completion (NOWAIT option)

For those batch data interchange commands that cause terminal control output requests to be made, the NOWAIT option can be specified. This option has the effect of allowing CICS task processing to continue; unless the NOWAIT option is specified, task activity is suspended until the batch data interchange command is completed. The NOWAIT option can be specified only on the ISSUE ADD, ISSUE ERASE, ISSUE REPLACE, and ISSUE SEND commands.

After a batch data interchange command with the NOWAIT option has been issued, task activity can be suspended, by the ISSUE WAIT command, at a suitable point in the program to wait for the command to be completed.