ATTDSP

The data stream profile (ATTDSP) parameter is ignored when attaching QMODEL (ATTDPN=X'03'). During other input, the ATTDSP field indicates a specific IMS input component.

The input component is used to identify an input IMS LTERM from a set of LTERMs (LTERM subpool) allocated to the session. The input DSP value must indicate a valid input component (an IMS LTERM defined with the input component value), or the input is rejected.

Several internal IMS functions are associated with the LTERM defined for the input component. For example, the LTERM defines a particular origin (input) and destination (output) path within IMS. This output destination can be the same as, or different from, the input origin LTERM and represents a stable application and operator reference point within IMS.

For statically defined terminals, input terminal security can be defined for the input LTERM. This security authorization can be unique for each LTERM or can represent a security level, or group, within IMS. Input terminal security authorizes access to IMS terminals, transactions, and commands.

The input ATTACH DSP parameter remains in effect until it is:
  • Changed by another ATTACH
  • Reset by a system failure
  • Backed out to its value at the last sync point by the ERP
  • Reset at between-brackets state
  • Reset by the RAP FM header

The input reset state for the ATTDSP parameter is X'00' or component 1.

Because IMS does not remember the active input ATTDSP across IMS system failures, the ATTDSP must be provided using an ATTACH FM header to restore the receiving process after a bind or negotiable bind response indicating in-brackets (possible restart).

The output LTERM is determined by either the LTERM selected for input or by the message sender, as for message switches and broadcast messages. IMS also allows the receiving message processing program (MPP) to change the destination of resulting output by issuing a CHNG call and inserting the output to a modifiable alternate PCB. For all system messages resulting directly from input (for example, commands), the output LTERM selected is the normal destination LTERM defined for the LTERM from which the input originated.

During output, the DSP field is set to the output component value associated with the output LTERM.

IMS Message Format Service can be defined as available on a component-by-component basis. The output component also specifies the bracket and send/receive protocol to be used for asynchronous output sent using the ATTACH having a DPN parameter indicating SCHEDULER.