DB2 Program Structure

A DB2 COBOL program follows the standard COBOL division structure, with DB2-specific pieces added: INCLUDE SQLCA and DCLGEN copybooks in WORKING-STORAGE, cursor DECLAREs in the DATA DIVISION, and EXEC SQL statements with SQLCODE checks in the PROCEDURE DIVISION.

The divisions of a DB2 program

• IDENTIFICATION DIVISION: PROGRAM-ID as usual. Nothing DB2-specific here.
• ENVIRONMENT DIVISION: file and device descriptions as usual. DB2 tables need no SELECT/ASSIGN entries.
• DATA DIVISION, WORKING-STORAGE: EXEC SQL INCLUDE SQLCA END-EXEC first, then DCLGEN copybook INCLUDEs, then host variable declarations, then EXEC SQL DECLARE CURSOR statements.
• PROCEDURE DIVISION: program logic with EXEC SQL blocks (OPEN, FETCH, CLOSE, SELECT, INSERT, UPDATE, DELETE, COMMIT), checking SQLCODE after each one.

DCLGEN: generated declarations

• DCLGEN (Declarations Generator) is a DB2I facility that generates the SQL DECLARE TABLE statement and matching COBOL host variable declarations for a table.
• The output is stored as a copybook member and pulled in with EXEC SQL INCLUDE member-name END-EXEC.
• Using DCLGEN guarantees the host variables match the table definition exactly, avoiding -310 mismatches.
• Regenerate the DCLGEN copybook whenever the table definition changes (ALTER TABLE).

Standard paragraph flow

• MAIN-PARA drives the program: open the cursor, fetch in a loop until SQLCODE is not 0, close the cursor, COMMIT, STOP RUN.
• OPEN-PARA opens the cursor and stops the program if SQLCODE is not 0.
• FETCH-PARA fetches one row; on SQLCODE 0 process the row, on 100 end the loop, otherwise display the error and stop.
• CLOSE-PARA closes the cursor to release DB2 resources.

Example of a complete DB2 COBOL program skeleton:-