ATTDPN

The destination process name (ATTDPN) parameter identifies, explicitly or implicitly, the input process to be attached to the half session.

One responsibility of the attached process is to determine, for the receiving subsystem, the destination of the input message within that subsystem. In some cases, the named process might be the message destination. Within IMS, the receiving process (except basic edit) uses the input primary resource name (ATTPRN), if provided, as the message destination transaction queue or LTERM. If an ATTPRN is not provided, the standard IMS algorithm for determining message destination is used.

Related reading: For more information on the IMS algorithm for determining message destination, see IMS Version 15.2 System Administration under IMS Messages and Their Scheduling.

All attached processes execute synchronously with the session. However, some processes can schedule additional work to be done asynchronously within IMS. The process attached remains attached until it is:
  • Changed by another ATTACH
  • Backed out to its value at the last sync point by the ERP
  • Reset by the end-bracket indicator
  • Reset by the RAP FM header
  • Reset by a system failure

The input reset state for the ATTDPN parameter is ISCEDT.

Because IMS does not remember the active input ATTDPN across IMS system failures, the ATTDPN 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 ATTDPN parameter might indicate that the process to be attached is one of the following:
  • ISC edit (‘ISCEDT' or user-named alias)
  • IMS Basic Edit (‘BASICEDT')
  • MFS formatting (MFS MID name)
  • System Message (SYSMSG), X'01'
  • SCHEDULER model, X'02'
  • Queue model (QMODEL), X'03'

With the exception of MFS and QMODEL, these processes are always available. MFS is only available if defined for the input component (ATTDSP) during IMS system definition. If the ATTDPN is an MFS MID name and MFS is not available, the input message is rejected. QMODEL is available only following an MFS demand-paged output message.

ISCEDT (as well as the alias defined by the user for ISCEDT during IMS system definition) and BASICEDT are reserved names, and cannot be used as MFS MID or MOD names. Use of these names results in the use of the named process rather than an MFS process.

ISC edit is selected if no ATTACH FM header (or no ATTDPN) is supplied when the Attach manager is in reset state. The active process is used if no ATTACH FM header (or no ATTDPN) is supplied when the attach manager is not in the reset state.

IMS sets the output ATTDPN on a return reply to the value contained in the ATTRDPN parameter optionally provided within the ATTACH of the previous input request. When sending system messages, IMS automatically inserts the SYSMSG ATTDPN where necessary. MFS DPM provides a way to optionally specify, override, or delete the output ATTDPN by using the output message format descriptor. When the ATTDPN parameter is not available for output, a 1-byte field containing X'00' is included within the output ATTACH FM header.