Overview of DL/I request handling in CICS

CICS® can access DL/I databases in the following ways:

Notes:
  1. Although these methods of accessing DL/I databases can coexist, a program specification block (PSB) can only contain databases that are controlled by one of the methods.
  2. CICS Transaction Server for OS/390®, Version 1 Release 1 onward does not support local DL/I.

CICS can also access DL/I databases in an IMS Database Manager/Transaction Manager (IMS DM/TM) system using the CICS-DBCTL interface. This means that you can have access to DL/I databases controlled by IMS DM/TM without needing to use IMS data sharing, provided that CICS and IMS DM/TM are in the same MVS™ image. Both the IMS DM/TM system and the CICS system can include the extended recovery facility (XRF).

Figure 1 illustrates the three kinds of DL/I request.

Figure 1. DL/I request handling within CICS
 This figure shows the three kinds of DL/I request:   A DBCTL request from CICS A via DBCTL A to DBCTL A’s database (Request #1). A remote (function shipped) request from CICS A to CICS B, to a database controlled by CICS B (Request #2a). A remote (function shipped) request from CICS A to CICS B, via DBCTL B connected to CICS B, to DBCTL B's database (Request #2b).

Notes:
  1. Request #1 is a DBCTL request from CICS A to DBCTL A for a database controlled by DBCTL A. See CICS-DL/I router (DFHDLI) for a description of request processing.
  2. Requests #2a and #2b are two separate remote (function shipped) DL/I requests to databases controlled by, or connected to, other CICS systems (which may be in the same MVS image or a different one). There are two ways of issuing such requests:
    • Request #2a from CICS A to CICS B for a database controlled by CICS B, where CICS B is CICS/ESA 4.1 or below
    • Request #2b from CICS A to CICS B for a database controlled by DBCTL B. The most likely reason for using request #2b is if CICS A and CICS B are in different MVS images.

Related concepts
Overview of Database Control (DBCTL)
Summary of the benefits of DBCTL
Connecting to DBCTL
CICS-IMS DBCTL environment
Coordinator control subsystem (CCTL)
Resources you can access from a CICS environment that includes DBCTL
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