What are the four main COBOL record operations?

The four main COBOL record operations are READ, WRITE, REWRITE, and DELETE. READ retrieves records from a file, WRITE adds new records, REWRITE updates existing records, and DELETE removes records from a file. Each operation requires the file to be opened in the appropriate mode and handles errors through file status codes or exception conditions.

What file modes are required for each record operation?

READ requires INPUT or I-O mode. WRITE requires OUTPUT, I-O, or EXTEND mode (OUTPUT creates/overwrites, EXTEND appends to sequential files, I-O allows writing to indexed/relative files). REWRITE requires I-O mode and the record must be read first. DELETE requires I-O mode and works with indexed or relative files.

What is the difference between WRITE and REWRITE?

WRITE adds a new record to a file, while REWRITE updates an existing record that was previously read. WRITE is used for creating new records, while REWRITE is used for updating existing records. Before using REWRITE, you must first READ the record you want to update, modify it in memory, then REWRITE it back to the file.

How do you handle errors in COBOL record operations?

Errors in COBOL record operations are handled through file status codes (FILE STATUS clause) or exception conditions (AT END, INVALID KEY, NOT AT END, NOT INVALID KEY). File status codes provide specific error information (like "00" for success, "23" for duplicate key, "10" for end of file), while exception conditions allow you to handle specific error scenarios in your program logic.

Can you use DELETE with sequential files?

No, DELETE cannot be used with sequential files. DELETE only works with indexed files (VSAM KSDS) and relative files (VSAM RRDS). For sequential files, you must create a new file excluding the records you want to delete, as sequential files do not support in-place deletion.

What is the difference between sequential and random access for READ operations?

Sequential access reads records one after another in order using READ NEXT or just READ, advancing through the file automatically. Random access reads a specific record by its key value using READ with a key specified, allowing you to jump directly to any record without reading through preceding records. Sequential is faster for processing entire files, while random is better for looking up specific records.

What happens if you try to REWRITE without reading first?

Attempting to REWRITE without first reading the record will result in an error. The file status will indicate an invalid operation (typically "24" or similar), and the REWRITE will fail. You must always READ a record before you can REWRITE it, as REWRITE replaces the last record that was read.

How do you append records to a sequential file?

To append records to a sequential file, open the file in EXTEND mode instead of OUTPUT mode. OUTPUT mode creates a new file or overwrites an existing one, while EXTEND mode opens the file for appending and positions the file pointer at the end, allowing you to WRITE new records that will be added after the existing records.

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COBOL Tutorial

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COBOL Record Operations

Record operations are fundamental to COBOL file processing. They allow you to interact with files by reading existing records, writing new ones, updating existing records, and deleting records. Understanding how to use READ, WRITE, REWRITE, and DELETE statements correctly is essential for effective file management in COBOL programs.

Each record operation has specific requirements regarding file modes, access methods, and error handling. This tutorial covers all four main record operations in detail, with practical examples and best practices for each.

Overview of Record Operations

COBOL provides four primary record operations for file manipulation:

READ - Retrieves records from a file
WRITE - Adds new records to a file
REWRITE - Updates existing records in a file
DELETE - Removes records from a file

Each operation requires the file to be opened in an appropriate mode and handles errors through file status codes or exception conditions. The choice of operation depends on your file organization (sequential, indexed, or relative) and access mode (sequential, random, or dynamic).

The READ Statement

The READ statement retrieves records from a file. It can be used with sequential, random, or dynamic access modes, depending on your file organization and how you want to access the data.

Sequential READ

Sequential READ reads records one after another in order. It's the most common method for processing entire files from beginning to end.

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IDENTIFICATION DIVISION.
PROGRAM-ID. READ-SEQUENTIAL-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 END-OF-FILE     VALUE "10".
   88 SUCCESS         VALUE "00".
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN INPUT CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM READ-RECORDS UNTIL END-OF-FILE
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
READ-RECORDS.
    READ CUSTOMER-FILE
        AT END
            DISPLAY "End of file reached"
            MOVE "10" TO FILE-STATUS-CODE
        NOT AT END
            DISPLAY "Customer ID: " CUST-ID
            DISPLAY "Customer Name: " CUST-NAME
            DISPLAY "Balance: " CUST-BALANCE
    END-READ.

In this example, the file is opened in INPUT mode for sequential access. The READ statement retrieves records one at a time. The AT END clause handles the end-of-file condition, while NOT AT END processes each successfully read record. The file status code "10" indicates end of file.

Random READ

Random READ allows you to read a specific record by its key value. This is useful for indexed files where you need to look up specific records without reading through the entire file.

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IDENTIFICATION DIVISION.
PROGRAM-ID. READ-RANDOM-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS RANDOM
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 RECORD-FOUND    VALUE "00".
   88 RECORD-NOT-FOUND VALUE "23".
01 SEARCH-ID          PIC 9(5).
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN INPUT CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    DISPLAY "Enter customer ID to search: "
    ACCEPT SEARCH-ID
    
    MOVE SEARCH-ID TO CUST-ID
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer " SEARCH-ID " not found"
        NOT INVALID KEY
            DISPLAY "Customer found:"
            DISPLAY "  Name: " CUST-NAME
            DISPLAY "  Balance: " CUST-BALANCE
    END-READ
    
    CLOSE CUSTOMER-FILE
    STOP RUN.

In random access mode, you set the key value (CUST-ID) before reading. The READ statement uses this key to locate the specific record. The INVALID KEY clause handles cases where the record doesn't exist (file status "23"), while NOT INVALID KEY processes the found record.

Dynamic READ with READ NEXT

Dynamic access mode allows you to switch between sequential and random access. You can use READ for random access and READ NEXT for sequential access within the same program.

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IDENTIFICATION DIVISION.
PROGRAM-ID. READ-DYNAMIC-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS DYNAMIC
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 END-OF-FILE     VALUE "10".
01 START-ID           PIC 9(5) VALUE 10000.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN INPUT CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    *> Start sequential read from a specific key
    MOVE START-ID TO CUST-ID
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Starting key not found, reading from beginning"
            START CUSTOMER-FILE KEY >= CUST-ID
                INVALID KEY
                    DISPLAY "Error positioning file"
                NOT INVALID KEY
                    PERFORM READ-SEQUENTIALLY
            END-START
        NOT INVALID KEY
            DISPLAY "Starting from customer: " CUST-NAME
            PERFORM READ-SEQUENTIALLY
    END-READ
    
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
READ-SEQUENTIALLY.
    PERFORM UNTIL END-OF-FILE
        READ CUSTOMER-FILE NEXT
            AT END
                DISPLAY "End of file reached"
            NOT AT END
                DISPLAY "Customer: " CUST-NAME " Balance: " CUST-BALANCE
        END-READ
    END-PERFORM.

Dynamic access provides flexibility by allowing both random and sequential operations. You can position the file at a specific key using START, then read sequentially from that point using READ NEXT. This is useful for processing ranges of records or starting sequential processing from a specific point.

The WRITE Statement

The WRITE statement adds new records to a file. The file mode determines how WRITE behaves: OUTPUT mode creates or overwrites a file, EXTEND mode appends to an existing sequential file, and I-O mode allows writing to indexed or relative files.

WRITE to Sequential File (OUTPUT Mode)

When opening a file in OUTPUT mode, WRITE creates new records. If the file exists, it will be overwritten.

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IDENTIFICATION DIVISION.
PROGRAM-ID. WRITE-OUTPUT-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
01 RECORD-COUNT       PIC 9(5) VALUE 0.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN OUTPUT CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM WRITE-RECORDS UNTIL RECORD-COUNT >= 10
    CLOSE CUSTOMER-FILE
    DISPLAY "Wrote " RECORD-COUNT " records"
    STOP RUN.
 
WRITE-RECORDS.
    ADD 1 TO RECORD-COUNT
    MOVE RECORD-COUNT TO CUST-ID
    MOVE "Customer Name " TO CUST-NAME
    MOVE ZEROS TO CUST-BALANCE
    
    WRITE CUSTOMER-RECORD
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error writing record: " FILE-STATUS-CODE
       STOP RUN
    END-IF.

In OUTPUT mode, each WRITE adds a new record to the file. The records are written in the order they are executed. If the file already exists, it will be replaced with the new data.

WRITE to Sequential File (EXTEND Mode)

EXTEND mode allows you to append records to an existing sequential file without losing existing data.

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IDENTIFICATION DIVISION.
PROGRAM-ID. WRITE-EXTEND-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    *> Open in EXTEND mode to append records
    OPEN EXTEND CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    *> Write new records that will be appended
    MOVE 10001 TO CUST-ID
    MOVE "New Customer 1" TO CUST-NAME
    MOVE 1500.50 TO CUST-BALANCE
    WRITE CUSTOMER-RECORD
    
    MOVE 10002 TO CUST-ID
    MOVE "New Customer 2" TO CUST-NAME
    MOVE 2300.75 TO CUST-BALANCE
    WRITE CUSTOMER-RECORD
    
    CLOSE CUSTOMER-FILE
    DISPLAY "Records appended successfully"
    STOP RUN.

EXTEND mode positions the file pointer at the end of the file, so all WRITE operations append new records after the existing ones. This is useful for adding new data without recreating the entire file.

WRITE to Indexed File (I-O Mode)

For indexed files, you can write new records when the file is opened in I-O mode. The system checks for duplicate keys and handles them according to your file definition.

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IDENTIFICATION DIVISION.
PROGRAM-ID. WRITE-INDEXED-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS RANDOM
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 SUCCESS         VALUE "00".
   88 DUPLICATE-KEY   VALUE "22".
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN I-O CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM ADD-CUSTOMER
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
ADD-CUSTOMER.
    DISPLAY "Enter customer ID: "
    ACCEPT CUST-ID
    DISPLAY "Enter customer name: "
    ACCEPT CUST-NAME
    DISPLAY "Enter balance: "
    ACCEPT CUST-BALANCE
    
    WRITE CUSTOMER-RECORD
        INVALID KEY
            IF DUPLICATE-KEY
                DISPLAY "Customer ID " CUST-ID " already exists"
            ELSE
                DISPLAY "Error writing record: " FILE-STATUS-CODE
            END-IF
        NOT INVALID KEY
            DISPLAY "Customer added successfully"
    END-WRITE.

When writing to an indexed file, the system checks if a record with the same key already exists. If it does, the INVALID KEY condition is triggered with file status "22" (duplicate key). The NOT INVALID KEY clause handles successful writes.

The REWRITE Statement

The REWRITE statement updates an existing record in a file. Before using REWRITE, you must first READ the record you want to update. REWRITE replaces the last record that was read.

REWRITE with Sequential Access

For sequential files, REWRITE updates the last record that was read. This is useful for updating records as you process a file sequentially.

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IDENTIFICATION DIVISION.
PROGRAM-ID. REWRITE-SEQUENTIAL-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.DAT"
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 END-OF-FILE     VALUE "10".
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN I-O CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM UPDATE-RECORDS UNTIL END-OF-FILE
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
UPDATE-RECORDS.
    READ CUSTOMER-FILE
        AT END
            CONTINUE
        NOT AT END
            *> Update balance for customers with ID less than 5000
            IF CUST-ID < 5000
                ADD 100.00 TO CUST-BALANCE
                REWRITE CUSTOMER-RECORD
                    IF FILE-STATUS-CODE NOT = "00"
                        DISPLAY "Error rewriting record: " FILE-STATUS-CODE
                    ELSE
                        DISPLAY "Updated customer " CUST-ID
                    END-IF
            END-IF
    END-READ.

In sequential access, you read records one by one. When you find a record that needs updating, you modify it in memory and use REWRITE to write it back. REWRITE replaces the record at the current file position (the last record read).

REWRITE with Random Access

For indexed files with random access, you read a specific record by key, modify it, then rewrite it.

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IDENTIFICATION DIVISION.
PROGRAM-ID. REWRITE-RANDOM-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS RANDOM
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 RECORD-FOUND    VALUE "00".
   88 RECORD-NOT-FOUND VALUE "23".
01 SEARCH-ID          PIC 9(5).
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN I-O CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM UPDATE-CUSTOMER
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
UPDATE-CUSTOMER.
    DISPLAY "Enter customer ID to update: "
    ACCEPT SEARCH-ID
    
    MOVE SEARCH-ID TO CUST-ID
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer " SEARCH-ID " not found"
        NOT INVALID KEY
            DISPLAY "Current information:"
            DISPLAY "  Name: " CUST-NAME
            DISPLAY "  Balance: " CUST-BALANCE
            
            DISPLAY "Enter new name (or press ENTER to keep current): "
            ACCEPT CUST-NAME
            
            DISPLAY "Enter new balance: "
            ACCEPT CUST-BALANCE
            
            REWRITE CUSTOMER-RECORD
                INVALID KEY
                    DISPLAY "Error updating record: " FILE-STATUS-CODE
                NOT INVALID KEY
                    DISPLAY "Customer updated successfully"
            END-REWRITE
    END-READ.

In random access mode, you specify the key of the record you want to update, read it, modify the data, and then rewrite it. This is the most common pattern for updating specific records in indexed files.

The DELETE Statement

The DELETE statement removes records from indexed or relative files. DELETE cannot be used with sequential files. For sequential access, you must read the record first; for random access, you can delete by key.

DELETE with Sequential Access

When using sequential access, you must read the record before you can delete it.

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IDENTIFICATION DIVISION.
PROGRAM-ID. DELETE-SEQUENTIAL-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS SEQUENTIAL
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
   05 CUST-STATUS     PIC X.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 END-OF-FILE     VALUE "10".
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN I-O CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM DELETE-INACTIVE-CUSTOMERS UNTIL END-OF-FILE
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
DELETE-INACTIVE-CUSTOMERS.
    READ CUSTOMER-FILE
        AT END
            CONTINUE
        NOT AT END
            *> Delete customers with status 'I' (Inactive)
            IF CUST-STATUS = "I"
                DELETE CUSTOMER-FILE RECORD
                    INVALID KEY
                        DISPLAY "Error deleting customer " CUST-ID
                    NOT INVALID KEY
                        DISPLAY "Deleted inactive customer " CUST-ID
                END-DELETE
            END-IF
    END-READ.

In sequential access, you read each record and check if it should be deleted. If so, you use DELETE to remove it. The DELETE statement removes the last record that was read.

DELETE with Random Access

With random access, you can delete a record directly by its key without reading it first (though reading first is often recommended to verify the record exists).

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IDENTIFICATION DIVISION.
PROGRAM-ID. DELETE-RANDOM-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS RANDOM
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-BALANCE    PIC S9(7)V99.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 RECORD-NOT-FOUND VALUE "23".
01 SEARCH-ID          PIC 9(5).
01 CONFIRM-DELETE     PIC X.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    OPEN I-O CUSTOMER-FILE
    IF FILE-STATUS-CODE NOT = "00"
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       STOP RUN
    END-IF
    
    PERFORM DELETE-CUSTOMER
    CLOSE CUSTOMER-FILE
    STOP RUN.
 
DELETE-CUSTOMER.
    DISPLAY "Enter customer ID to delete: "
    ACCEPT SEARCH-ID
    
    *> Read first to display information and confirm
    MOVE SEARCH-ID TO CUST-ID
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer " SEARCH-ID " not found"
        NOT INVALID KEY
            DISPLAY "Customer to delete:"
            DISPLAY "  Name: " CUST-NAME
            DISPLAY "  Balance: " CUST-BALANCE
            DISPLAY "Are you sure? (Y/N): "
            ACCEPT CONFIRM-DELETE
            
            IF CONFIRM-DELETE = "Y"
                DELETE CUSTOMER-FILE RECORD
                    INVALID KEY
                        DISPLAY "Error deleting customer: " FILE-STATUS-CODE
                    NOT INVALID KEY
                        DISPLAY "Customer " SEARCH-ID " deleted successfully"
                END-DELETE
            ELSE
                DISPLAY "Deletion cancelled"
            END-IF
    END-READ.

In random access mode, you can delete by key. It's good practice to read the record first to display its information and get user confirmation before deleting. This prevents accidental deletions and provides better user feedback.

Complete Example: File Maintenance Program

Here's a complete example that demonstrates all four record operations in a customer maintenance program:

cobol

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IDENTIFICATION DIVISION.
PROGRAM-ID. CUSTOMER-MAINTENANCE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO "CUSTOMER.IDX"
        ORGANIZATION IS INDEXED
        ACCESS MODE IS DYNAMIC
        RECORD KEY IS CUST-ID
        FILE STATUS IS FILE-STATUS-CODE.
 
DATA DIVISION.
FILE SECTION.
FD CUSTOMER-FILE.
01 CUSTOMER-RECORD.
   05 CUST-ID         PIC 9(5).
   05 CUST-NAME       PIC X(30).
   05 CUST-ADDRESS    PIC X(50).
   05 CUST-BALANCE    PIC S9(7)V99.
   05 CUST-STATUS     PIC X.
 
WORKING-STORAGE SECTION.
01 FILE-STATUS-CODE   PIC XX.
   88 SUCCESS         VALUE "00".
   88 END-OF-FILE     VALUE "10".
   88 RECORD-NOT-FOUND VALUE "23".
   88 DUPLICATE-KEY   VALUE "22".
 
01 MENU-CHOICE        PIC 9.
   88 ADD-RECORD      VALUE 1.
   88 UPDATE-RECORD   VALUE 2.
   88 DELETE-RECORD   VALUE 3.
   88 DISPLAY-RECORD  VALUE 4.
   88 LIST-ALL        VALUE 5.
   88 EXIT-PROGRAM    VALUE 9.
 
01 CONTINUE-FLAG      PIC X VALUE "Y".
   88 EXIT-APP        VALUE "N".
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    PERFORM INITIALIZATION
    PERFORM UNTIL EXIT-APP
        PERFORM DISPLAY-MENU
        PERFORM PROCESS-MENU-CHOICE
    END-PERFORM
    PERFORM TERMINATION
    STOP RUN.
 
INITIALIZATION.
    OPEN I-O CUSTOMER-FILE
    IF NOT SUCCESS
       DISPLAY "Error opening file: " FILE-STATUS-CODE
       MOVE "N" TO CONTINUE-FLAG
    END-IF.
 
DISPLAY-MENU.
    DISPLAY " "
    DISPLAY "CUSTOMER MAINTENANCE MENU"
    DISPLAY "1. Add Customer"
    DISPLAY "2. Update Customer"
    DISPLAY "3. Delete Customer"
    DISPLAY "4. Display Customer"
    DISPLAY "5. List All Customers"
    DISPLAY "9. Exit"
    DISPLAY "Enter choice: "
    ACCEPT MENU-CHOICE.
 
PROCESS-MENU-CHOICE.
    EVALUATE TRUE
        WHEN ADD-RECORD
            PERFORM ADD-CUSTOMER
        WHEN UPDATE-RECORD
            PERFORM UPDATE-CUSTOMER
        WHEN DELETE-RECORD
            PERFORM DELETE-CUSTOMER
        WHEN DISPLAY-RECORD
            PERFORM DISPLAY-CUSTOMER
        WHEN LIST-ALL
            PERFORM LIST-CUSTOMERS
        WHEN EXIT-PROGRAM
            MOVE "N" TO CONTINUE-FLAG
        WHEN OTHER
            DISPLAY "Invalid choice"
    END-EVALUATE.
 
ADD-CUSTOMER.
    DISPLAY "Enter customer ID: "
    ACCEPT CUST-ID
    DISPLAY "Enter customer name: "
    ACCEPT CUST-NAME
    DISPLAY "Enter address: "
    ACCEPT CUST-ADDRESS
    DISPLAY "Enter balance: "
    ACCEPT CUST-BALANCE
    MOVE "A" TO CUST-STATUS
    
    WRITE CUSTOMER-RECORD
        INVALID KEY
            IF DUPLICATE-KEY
                DISPLAY "Customer ID " CUST-ID " already exists"
            ELSE
                DISPLAY "Error adding customer: " FILE-STATUS-CODE
            END-IF
        NOT INVALID KEY
            DISPLAY "Customer added successfully"
    END-WRITE.
 
UPDATE-CUSTOMER.
    DISPLAY "Enter customer ID to update: "
    ACCEPT CUST-ID
    
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer " CUST-ID " not found"
        NOT INVALID KEY
            DISPLAY "Current information:"
            DISPLAY "  Name: " CUST-NAME
            DISPLAY "  Address: " CUST-ADDRESS
            DISPLAY "  Balance: " CUST-BALANCE
            
            DISPLAY "Enter new name (or ENTER to keep): "
            ACCEPT CUST-NAME
            
            DISPLAY "Enter new address (or ENTER to keep): "
            ACCEPT CUST-ADDRESS
            
            DISPLAY "Enter new balance: "
            ACCEPT CUST-BALANCE
            
            REWRITE CUSTOMER-RECORD
                INVALID KEY
                    DISPLAY "Error updating customer: " FILE-STATUS-CODE
                NOT INVALID KEY
                    DISPLAY "Customer updated successfully"
            END-REWRITE
    END-READ.
 
DELETE-CUSTOMER.
    DISPLAY "Enter customer ID to delete: "
    ACCEPT CUST-ID
    
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer " CUST-ID " not found"
        NOT INVALID KEY
            DISPLAY "Customer to delete:"
            DISPLAY "  Name: " CUST-NAME
            DISPLAY "  Balance: " CUST-BALANCE
            DISPLAY "Confirm deletion (Y/N): "
            ACCEPT CONTINUE-FLAG
            
            IF CONTINUE-FLAG = "Y"
                DELETE CUSTOMER-FILE RECORD
                    INVALID KEY
                        DISPLAY "Error deleting customer: " FILE-STATUS-CODE
                    NOT INVALID KEY
                        DISPLAY "Customer deleted successfully"
                END-DELETE
            ELSE
                DISPLAY "Deletion cancelled"
            END-IF
    END-READ.
 
DISPLAY-CUSTOMER.
    DISPLAY "Enter customer ID: "
    ACCEPT CUST-ID
    
    READ CUSTOMER-FILE
        INVALID KEY
            DISPLAY "Customer " CUST-ID " not found"
        NOT INVALID KEY
            DISPLAY "Customer Information:"
            DISPLAY "  ID: " CUST-ID
            DISPLAY "  Name: " CUST-NAME
            DISPLAY "  Address: " CUST-ADDRESS
            DISPLAY "  Balance: " CUST-BALANCE
            DISPLAY "  Status: " CUST-STATUS
    END-READ.
 
LIST-CUSTOMERS.
    DISPLAY "Listing all customers..."
    MOVE ZEROS TO CUST-ID
    START CUSTOMER-FILE KEY >= CUST-ID
        INVALID KEY
            DISPLAY "Error positioning file"
        NOT INVALID KEY
            PERFORM UNTIL END-OF-FILE
                READ CUSTOMER-FILE NEXT
                    AT END
                        CONTINUE
                    NOT AT END
                        DISPLAY CUST-ID " - " CUST-NAME " - " CUST-BALANCE
                END-READ
            END-PERFORM
    END-START.
 
TERMINATION.
    CLOSE CUSTOMER-FILE
    DISPLAY "Program terminated.".

This comprehensive example demonstrates all four record operations in a single program. It uses dynamic access mode, which allows both sequential and random operations. The program provides a menu-driven interface for adding, updating, deleting, displaying, and listing customers.

File Status Codes

Understanding file status codes is crucial for proper error handling in record operations. Here are the most common codes:

Common COBOL File Status Codes
Status Code	Meaning	Applicable Operations
"00"	Successful operation	All operations
"10"	End of file reached	READ (sequential)
"22"	Duplicate key (record already exists)	WRITE (indexed files)
"23"	Record not found or invalid key	READ, REWRITE, DELETE (random access)
"24"	Boundary violation or invalid operation	REWRITE (without prior READ)
"30"	Permanent I/O error	All operations
"34"	Boundary violation (record too large)	WRITE, REWRITE

Best Practices

Follow these best practices when working with COBOL record operations:

1. Always Check File Status

Always check the file status code after each operation to ensure it completed successfully. Don't assume operations will always succeed.

2. Use Appropriate File Modes

Choose the correct file mode for your operations:

Use INPUT for read-only access
Use OUTPUT for creating new files
Use EXTEND for appending to sequential files
Use I-O for files that need updating or deletion

3. Read Before REWRITE

Always READ a record before attempting to REWRITE it. REWRITE replaces the last record that was read, so you must read first to establish which record will be updated.

4. Handle End-of-File Conditions

When processing files sequentially, always check for end-of-file conditions using AT END or file status "10" to prevent reading past the end of the file.

5. Validate Keys Before Operations

For random access operations, validate that key values are within acceptable ranges and formats before attempting READ, WRITE, REWRITE, or DELETE operations.

6. Use Dynamic Access When Appropriate

Use dynamic access mode when your program needs both sequential and random access. This provides flexibility without requiring multiple file opens.

7. Close Files Properly

Always close files when you're done with them. This ensures all buffers are flushed and resources are released properly.

Common Errors and Solutions

Error: Attempting REWRITE Without Reading First

Problem: Trying to REWRITE a record without first reading it results in file status "24" (boundary violation).

Solution: Always READ the record you want to update before using REWRITE.

Error: Using DELETE with Sequential Files

Problem: DELETE cannot be used with sequential file organization.

Solution: Use indexed or relative file organization if you need DELETE functionality, or create a new file excluding records you want to delete.

Error: Duplicate Key on WRITE

Problem: Attempting to WRITE a record with a key that already exists results in file status "22".

Solution: Check if the record exists first using READ, or handle the INVALID KEY condition and inform the user.

Error: Reading Past End of File

Problem: Continuing to read after reaching end of file causes errors.

Solution: Always check for AT END condition or file status "10" and exit your read loop when end of file is reached.

Summary

COBOL record operations provide the foundation for file processing. Understanding READ, WRITE, REWRITE, and DELETE statements, along with their requirements for file modes and access methods, is essential for effective file management. Always handle errors properly using file status codes or exception conditions, and follow best practices to ensure reliable and maintainable code.

Remember that each operation has specific requirements:

READ requires INPUT or I-O mode
WRITE requires OUTPUT, EXTEND, or I-O mode
REWRITE requires I-O mode and a prior READ
DELETE requires I-O mode and works only with indexed or relative files

By mastering these operations and understanding their proper usage, you can build robust file processing applications in COBOL.

Test Your Knowledge

1. Which file mode is required to use the REWRITE statement?

INPUT mode
OUTPUT mode
I-O mode
EXTEND mode

2. What must you do before using REWRITE to update a record?

Open the file in OUTPUT mode
Read the record you want to update
Delete the old record first
Write a new record

3. Which record operation can be used with sequential files?

DELETE
REWRITE
READ and WRITE
All of the above

4. What file status code typically indicates a successful operation?

"00"
"10"
"23"
"99"

5. What is the difference between opening a file in OUTPUT mode vs EXTEND mode?

OUTPUT creates a new file, EXTEND appends to existing file
They are the same
OUTPUT is for reading, EXTEND is for writing
EXTEND is faster than OUTPUT

6. For which file organizations can you use the DELETE statement?

Sequential files only
Indexed and relative files
All file organizations
None - DELETE is not a COBOL statement

7. What happens when you READ a file that has reached the end?

The program crashes
The AT END condition is triggered
The last record is read again
A new file is created

8. In random access mode, how do you specify which record to READ?

By record number
By setting the record key before reading
By using READ NEXT
You cannot specify which record to read

COBOL Tutorial

COBOL Record Operations

Overview of Record Operations

The READ Statement

Sequential READ

Random READ

Dynamic READ with READ NEXT

The WRITE Statement

WRITE to Sequential File (OUTPUT Mode)

WRITE to Sequential File (EXTEND Mode)

WRITE to Indexed File (I-O Mode)

The REWRITE Statement

REWRITE with Sequential Access

REWRITE with Random Access

The DELETE Statement

DELETE with Sequential Access

DELETE with Random Access

Complete Example: File Maintenance Program

File Status Codes

Best Practices

1. Always Check File Status

2. Use Appropriate File Modes

3. Read Before REWRITE

4. Handle End-of-File Conditions

5. Validate Keys Before Operations

6. Use Dynamic Access When Appropriate

7. Close Files Properly

Common Errors and Solutions

Error: Attempting REWRITE Without Reading First

Error: Using DELETE with Sequential Files

Error: Duplicate Key on WRITE

Error: Reading Past End of File

Summary

Test Your Knowledge

Related Concepts

COBOL File Processing

COBOL File Status Error Handling

COBOL Indexed File Operations

COBOL Sequential File Operations

Related Pages