How IMS determines which queues to allocate

IMS uses the following method to determine which LTERMs to allocate.

  1. If the user control blocks already exist within IMS, these control blocks are reallocated, and the Signon exit routine is called, if appropriate.
  2. If the control blocks do not exist and a user descriptor is specified at signon, IMS looks for the specified descriptor.
    • If the descriptor specified is not the user ID, node name, or DFSUSER descriptor, IMS sends error message DFS3649A (with return code 148).
    • If the descriptor specified is a valid user descriptor for the user that is signing on, IMS builds a table of available descriptors and calls the Signon exit routine, if appropriate.
    • If the Signon exit routine exists and RC=0, IMS continues normal signon processing. If the return code does not equal 0, the signon is rejected.
  3. If no user descriptor is specified at signon and no user descriptor is specified in the Signon exit routine, IMS chooses a valid descriptor from the following (in order):
    1. User ID
    2. Node name
    3. DFSUSER