These four diagrams illustrate
the external
CICS®
interface using the EXCI CALL interface.
Figure 1. Stage 1: Status after an INITIALIZE_USER call
Note:
In Figure 1, the target CICS region is running with IRC open, and
one EXCI connection with three sessions installed, at the time the client
application program issues an INITIALIZE_USER call.
The client application program address space is initialized with the EXCI
user environment. There is no MRO activity at this stage, and no pipe exists.
Figure 2. Stage 2: Status after the first ALLOCATE_PIPE call
Note: In Figure 2, the external CICS interface logs on to MRO, identifying the target CICS server region.
Figure 3. Stage 3: Status after the OPEN_PIPE call
Note:
In Figure 3, the external CICS interface connects to the CICS server region,
and the pipe is now available for use.
The remaining two EXCI sessions are free, and can be used by further open
pipe requests from the same, or a different, client application program (provided
the connection is generic).
Figure 4. Stage 4: Status with one open pipe, processing a DPL call
Note: In Figure 4, the external CICS interface passes
the DPL request over the open pipe, with any associated data. The CICS server region
returns a response and data over the open pipe.
Closing pipes: When the client application
program closes a pipe, it remains allocated ready for use by the same user,
and the status is as shown in Figure 2. At this stage, the MRO
session is available for use by another open pipe request, from the same or
from a different client application program (provided the connection is generic).
Deallocating pipes: When the client application
program deallocates a pipe, it logs off from MRO and frees all the storage
associated with the session. This leaves the status as shown in Figure 1.
