CA IDMS VSAM Transparency User Exits › COBOL User Exit Program › Program Requirements

Program Requirements

Quasi-Reentrant Exit

The exit must be quasi-reentrant. Under central version, this requires no additional processing. Under local mode, the exit must initialize all work fields programmatically. A quasireentrant program retains the working storage values last set by a previous call to the program. CA IDMS/DB and CA IDMS VSAM Transparency do not re-initialize the fields when executing in local mode.

ENVIRONMENT DIVISION

In the ENVIRONMENT DIVISION, specify MODE IS BATCH, even if the exit is to run under CA IDMS/DC.

LINKAGE SECTION

In the LINKAGE SECTION, include:

• The user exit control block used to obtain information from CA IDMS VSAM Transparency that the user exit requires.
• The subschema control block that can be used by the user exit to perform its own DML calls for database access.
• The user record that the exit is building and storing. This is the record used by the VSAM program.

Example

LINKAGE SECTION.
01  USER-EXIT-CONTROL-BLOCK.
    .
    .
    .
COPY IDMS SUBSCHEMA-CTRL.
    .
    .
    .
01  USER-RECORD.
    .
    .
    .
PROCEDURE DIVISION
       USING USER-EXIT-CONTROL-BLOCK, SUBSCHEMA-CTRL, USER-RECORD.

PROCEDURE DIVISION

In the PROCEDURE DIVISION, do not copy SUBSCHEMA-BINDS. The rununit is bound prior to the exit receiving control. CA IDMS VSAM Transparency binds the record defined in the FMT the first time it attempts to access it. The exit must issue a bind only for additional records it needs.

• If the exit attempts to access the record defined in the FMT prior to CA IDMS VSAM Transparency, the exit must bind this record.
• The exit must issue a GOBACK when it is complete. It must not issue a STOP RUN.

More information:

For more information on coding CA IDMS/DB and DC/UCF programs see CA IDMS Navigational DML Programming Guide.

Compiling and Linking the Program

Compile and link the program once the user exit is complete and you have run the program through the DMLC preprocessor. Link the following modules with the exit:

INCLUDE libname(ESVSIDMS)
INCLUDE libname(IDMSBALI)

Note: Libname is the DD name of the file in the JCL that contains the CA IDMS/DB-supplied object modules.

Defining the Exit

Define the exit to CA IDMS/DB by including an ADD PROGRAM statement for the exit program in the system generation. The ADD PROGRAM statement should appear as follows:

ADD PROGRAM exitname
    LANGUAGE IS COBOL
    QUASIREENTRANT
    NOPROTECT.

Note: The exit accesses DC/UCF system control blocks, therefore storage protection must be off (NOPROTECT).