💬 Q&A Solutions

REDEFINES allows the same storage area to be referenced by different data names with different definitions.

Rules:

• Must be at same level as item being redefined
• Cannot redefine item with OCCURS
• Redefined item must appear first
• Lengths should match or redefining should be shorter

01 WS-DATE.
   05 WS-DATE-NUM    PIC 9(8).
01 WS-DATE-X REDEFINES WS-DATE.
   05 WS-YEAR        PIC 9(4).
   05 WS-MONTH       PIC 9(2).
   05 WS-DAY         PIC 9(2).

Same 8 bytes can be accessed as single number or individual components.

PARM (EXEC statement):

• Limited to 100 characters
• Passed in memory to program
• Accessed via LINKAGE SECTION
• Good for small, simple parameters

SYSIN (DD statement):

• No practical size limit
• Read as a file by program
• Can contain multiple records
• Good for control cards, complex input

// PARM example
//STEP1 EXEC PGM=MYPROG,PARM='PARAM1,PARAM2'

// SYSIN example
//SYSIN DD *
CONTROL OPTION1
DATE=20231215
LIMIT=1000
/*

INNER JOIN:

• Returns only matching rows from both tables
• If no match, row is excluded

LEFT OUTER JOIN:

• Returns all rows from left table
• Matching rows from right table
• NULL for right table if no match

-- INNER JOIN
SELECT E.NAME, D.DEPT_NAME
FROM EMPLOYEE E
INNER JOIN DEPARTMENT D
ON E.DEPT_ID = D.DEPT_ID;

-- LEFT OUTER JOIN
SELECT E.NAME, D.DEPT_NAME
FROM EMPLOYEE E
LEFT OUTER JOIN DEPARTMENT D
ON E.DEPT_ID = D.DEPT_ID;

Use LEFT JOIN when you want all employees even those without department.

COMMAREA (Communication Area) is used to pass data between programs or between transactions in pseudo-conversational programming.

Uses:

• Pass data between LINK/XCTL programs
• Save data between pseudo-conversational transactions
• Maximum size: 32KB

How it works:

1. Calling program: COMMAREA option on LINK/XCTL/RETURN
2. Called program: DFHCOMMAREA in LINKAGE SECTION
3. Check EIBCALEN for length (0 = no COMMAREA)

* Calling program
EXEC CICS LINK
    PROGRAM('SUBPROG')
    COMMAREA(WS-DATA)
    LENGTH(100)
END-EXEC.

* Called program
LINKAGE SECTION.
01 DFHCOMMAREA PIC X(100).

IF EIBCALEN > 0
    MOVE DFHCOMMAREA TO WS-DATA
END-IF.