TERMINAL macro

Several system definition keyword parameters on the TERMINAL macro are principal for defining an ISC session.

The principal system definition keyword parameters for defining an ISC session on the TERMINAL macro are as follows:
  • OUTBUF
  • MSGDEL
  • COMPT1
  • COMPT2
  • COMPT3
  • COMPT4
Additional parameters you must specify include:
  • SINGLE or MULT
  • VLVB or DPM-B1...DPM-B15

Specifying the OUTBUF= keyword parameter

IMS does not negotiate buffer sizes when initiating an ISC session, nor does IMS support RU truncation. When sending a negotiated bind, IMS sets its send (OUTBUF=) and receive (RECANY=) sizes in the bind.

When receiving the bind reply, IMS verifies that:
  • Its send (OUTBUF=) size has not been reduced by the other subsystem.
  • Its receive (RECANY=) size is not exceeded by the other subsystem's send (OUTBUF=) size.
When receiving a negotiated bind, IMS:
  • Verifies that the send (OUTBUF=) size of the other subsystem does not exceed IMS's receive (RECANY=) size.
  • Inserts the send (OUTBUF=) size into the bind reply.

The specified OUTBUF size must be large enough to include the largest output segment size plus the overhead for message headers. When defining the SFIMS system, the same considerations apply.

Specifying the MSGDEL= keyword parameter

A description of the ramifications of choosing SYSINFO or NONIOPCB is found in LTERM users (subpools) and components. In the example in that topic, the default for SYSINFO is used for both the TERMINAL and the SUBPOOL macros.

Specifying the COMPTn= keyword parameter

Up to four components can be defined for a given ISC node on the TERMINAL macro by using the keyword parameters COMPT1= through COMPT4=. COMPTn= allows flexibility in assigning characteristics to LTERMs. In the system definition example, component 1 is specified as having the characteristics SINGLE1, DPM-B1, and IGNORE. Component 2 is specified as having the characteristics SINGLE2, DPM-B2, and IGNORE.

Specifying the SINGLE or MULT parameter

The characteristics of SINGLE1, SINGLE2, MULT1, and MULT2 are described in Determining output protocols.

Specifying the VLVB or DPM-B1…DPM-B15 parameter

Selecting VLVB or DPM-Bn determines whether the component can use the Distributed Presentation Management feature of MFS. Although MFS is specified for a component by specifying DPM-Bn, its use is optional, on a message-by-message basis. DPM-Bn is used for this system definition example.

The selection of VLVB precludes the use of MFS-DPM for a component and indicates that variable-length, variable-blocked format is to be used instead of MFS for both input and output.

Specifying the IGNORE or 1, 2,…10 parameter

This parameter is used to specify a user-defined feature code for MFS DPM-Bn. The designated feature is used to select an MFS format (DPM-B1…DPM-B15) that contains the matching feature specification. IGNORE is used to specify that an MFS format (DPM-Bn) with the FEAT=IGNORE of the DEV statement is to be selected. IGNORE has been used for this system definition example.