The following types of DL/I requests can be made by a CICS® system:
CICS support for DL/I is provided as follows:
This component determines whether the call is using a remote or DBCTL PSB, and passes control to the appropriate call processor. This component is described in more detail later in this topic.
This component is subdivided into:
Each call processor deals with a specific interface that is described in the appropriate topic of this book for the remote DL/I function and the DBCTL function.
Figure 39 shows the relationships between the components of the CICS-DL/I interface.
If the request is for a remote database, DFHDLI passes control to DFHDLIRP. If the request is for a DBCTL database, DFHDLI passes control to DFHDLIDP.
In addition to processing DL/I input/output requests, the DL/I interface, on request, schedules and terminates DL/I program specification blocks (PSBs).
The remainder of this topic is concerned with the router component.
The router component receives a request in standard CALL DLI parameter lists. At schedule time, it determines whether the request is a remote or DBCTL request.
Amongst the functions of the router are the following:
At PSB schedule time, the router determines whether the DL/I requests issued from the application program should be routed to DBCTL or another CICS system (remote). The presence (or absence) of the PSB used in the PDIR determines where the call gets routed.
If no PDIR exists (that is, the PDIR=NO system initialization parameter is specified or is allowed to default), the request is routed to the DBCTL call processor.
If a PDIR has been specified, the router module scans the PDIR. All entries in the PDIR have a SYSIDNT option specified. If the PSB is not found in the PDIR, or if the PDIR entry specifies a SYSIDNT that is the SYSIDNT of the CICS system that is currently running, the request is routed to the DBCTL call processor. Otherwise, the request is routed to the remote call processor.
All DL/I requests are routed to the same DL/I call processor as the corresponding PSB schedule request in the same unit of work.
The router provides special handling of the DL/I TERM call. When the router detects a TERM call, it forces a syncpoint, causing CICS to carry out syncpoint processing for the task.
The router module generates CICS trace records at DL/I call entry and DL/I call exit.
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