COBOL SORT-MERGE Statement - Quick Reference

The SORT-MERGE statement in COBOL is used to combine multiple sorted input files into a single sorted output file. It maintains the sort order while efficiently merging data from multiple sources.

Primary Use

Merge multiple sorted files into single sorted output

Division

PROCEDURE DIVISION

File Type

Sequential files with SD definition

Performance

Efficient merging of pre-sorted files

Overview

The SORT-MERGE statement is a specialized COBOL feature that combines multiple sorted input files into a single sorted output file. It is designed for scenarios where you have multiple files that are already sorted in the same order and need to be combined into one file. SORT-MERGE maintains the sort order while efficiently processing multiple input streams.

Syntax

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SORT-MERGE sort-merge-file-name
    ON ASCENDING KEY merge-key-1 [merge-key-2 ...]
    ON DESCENDING KEY merge-key-3 [merge-key-4 ...]
    USING input-file-1 [input-file-2 ...]
    GIVING output-file-1 [output-file-2 ...]
    [OUTPUT PROCEDURE procedure-name-1 [THROUGH procedure-name-2]]

Practical Examples

Basic SORT-MERGE Operation

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* Basic SORT-MERGE with two input files
IDENTIFICATION DIVISION.
PROGRAM-ID. BASIC-SORT-MERGE-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT FILE-1 ASSIGN TO "FILE1.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT FILE-2 ASSIGN TO "FILE2.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT MERGED-FILE ASSIGN TO "MERGED.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT SORT-MERGE-WORK ASSIGN TO "SORTWORK".
 
DATA DIVISION.
FILE SECTION.
SD  SORT-MERGE-WORK.
01  SORT-MERGE-RECORD.
    05  MERGE-CUSTOMER-ID    PIC X(10).
    05  MERGE-CUSTOMER-NAME  PIC X(30).
    05  MERGE-BALANCE        PIC 9(8)V99.
 
FD  FILE-1.
01  FILE-1-RECORD.
    05  FILE-1-CUSTOMER-ID   PIC X(10).
    05  FILE-1-CUSTOMER-NAME PIC X(30).
    05  FILE-1-BALANCE       PIC 9(8)V99.
 
FD  FILE-2.
01  FILE-2-RECORD.
    05  FILE-2-CUSTOMER-ID   PIC X(10).
    05  FILE-2-CUSTOMER-NAME PIC X(30).
    05  FILE-2-BALANCE       PIC 9(8)V99.
 
FD  MERGED-FILE.
01  MERGED-RECORD.
    05  MERGED-CUSTOMER-ID   PIC X(10).
    05  MERGED-CUSTOMER-NAME PIC X(30).
    05  MERGED-BALANCE       PIC 9(8)V99.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    * Merge two sorted files by customer ID
    SORT-MERGE SORT-MERGE-WORK
        ON ASCENDING KEY MERGE-CUSTOMER-ID
        USING FILE-1, FILE-2
        GIVING MERGED-FILE
    
    DISPLAY "Sort-merge completed successfully"
    STOP RUN.

Explanation: This example demonstrates a basic SORT-MERGE operation that combines two sorted input files (FILE-1 and FILE-2) into a single sorted output file (MERGED-FILE). The merge is performed on the customer ID field in ascending order. Both input files must be pre-sorted by customer ID for the merge to work correctly.

Multi-Key SORT-MERGE Operation

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* Multi-key SORT-MERGE with mixed ordering
IDENTIFICATION DIVISION.
PROGRAM-ID. MULTI-KEY-SORT-MERGE-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT EAST-REGION-FILE ASSIGN TO "EAST.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT WEST-REGION-FILE ASSIGN TO "WEST.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT SOUTH-REGION-FILE ASSIGN TO "SOUTH.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT CONSOLIDATED-FILE ASSIGN TO "CONSOLIDATED.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT SORT-MERGE-WORK ASSIGN TO "SORTWORK".
 
DATA DIVISION.
FILE SECTION.
SD  SORT-MERGE-WORK.
01  SORT-MERGE-RECORD.
    05  MERGE-REGION          PIC X(2).
    05  MERGE-DEPARTMENT      PIC X(3).
    05  MERGE-EMPLOYEE-ID     PIC X(6).
    05  MERGE-SALARY          PIC 9(8)V99.
 
FD  EAST-REGION-FILE.
01  EAST-RECORD.
    05  EAST-REGION           PIC X(2).
    05  EAST-DEPARTMENT       PIC X(3).
    05  EAST-EMPLOYEE-ID      PIC X(6).
    05  EAST-SALARY           PIC 9(8)V99.
 
FD  WEST-REGION-FILE.
01  WEST-RECORD.
    05  WEST-REGION           PIC X(2).
    05  WEST-DEPARTMENT       PIC X(3).
    05  WEST-EMPLOYEE-ID      PIC X(6).
    05  WEST-SALARY           PIC 9(8)V99.
 
FD  SOUTH-REGION-FILE.
01  SOUTH-RECORD.
    05  SOUTH-REGION          PIC X(2).
    05  SOUTH-DEPARTMENT      PIC X(3).
    05  SOUTH-EMPLOYEE-ID     PIC X(6).
    05  SOUTH-SALARY          PIC 9(8)V99.
 
FD  CONSOLIDATED-FILE.
01  CONSOLIDATED-RECORD.
    05  CONSOLIDATED-REGION   PIC X(2).
    05  CONSOLIDATED-DEPT     PIC X(3).
    05  CONSOLIDATED-EMP-ID   PIC X(6).
    05  CONSOLIDATED-SALARY   PIC 9(8)V99.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    * Merge three region files by region (ascending), department (ascending), salary (descending)
    SORT-MERGE SORT-MERGE-WORK
        ON ASCENDING KEY MERGE-REGION
        ON ASCENDING KEY MERGE-DEPARTMENT
        ON DESCENDING KEY MERGE-SALARY
        USING EAST-REGION-FILE, WEST-REGION-FILE, SOUTH-REGION-FILE
        GIVING CONSOLIDATED-FILE
    
    DISPLAY "Multi-key sort-merge completed successfully"
    STOP RUN.

Explanation: This example demonstrates a multi-key SORT-MERGE operation that combines three region files using multiple sort keys. The merge is performed first by region (ascending), then by department (ascending), and finally by salary (descending) within each department. This creates a consolidated file with employees organized by region and department, with highest-paid employees listed first within each department.

SORT-MERGE with OUTPUT PROCEDURE

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* SORT-MERGE with OUTPUT PROCEDURE for custom processing
IDENTIFICATION DIVISION.
PROGRAM-ID. SORT-MERGE-OUTPUT-PROC-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT DAILY-FILE-1 ASSIGN TO "DAILY1.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT DAILY-FILE-2 ASSIGN TO "DAILY2.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT SUMMARY-FILE ASSIGN TO "SUMMARY.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT SORT-MERGE-WORK ASSIGN TO "SORTWORK".
 
DATA DIVISION.
FILE SECTION.
SD  SORT-MERGE-WORK.
01  SORT-MERGE-RECORD.
    05  MERGE-DATE            PIC X(8).
    05  MERGE-ACCOUNT         PIC X(10).
    05  MERGE-AMOUNT          PIC 9(8)V99.
    05  MERGE-TRANSACTION-TYPE PIC X(1).
 
FD  DAILY-FILE-1.
01  DAILY-1-RECORD.
    05  DAILY-1-DATE          PIC X(8).
    05  DAILY-1-ACCOUNT       PIC X(10).
    05  DAILY-1-AMOUNT        PIC 9(8)V99.
    05  DAILY-1-TRANS-TYPE    PIC X(1).
 
FD  DAILY-FILE-2.
01  DAILY-2-RECORD.
    05  DAILY-2-DATE          PIC X(8).
    05  DAILY-2-ACCOUNT       PIC X(10).
    05  DAILY-2-AMOUNT        PIC 9(8)V99.
    05  DAILY-2-TRANS-TYPE    PIC X(1).
 
FD  SUMMARY-FILE.
01  SUMMARY-RECORD.
    05  SUMMARY-LINE          PIC X(80).
 
WORKING-STORAGE SECTION.
01  WS-EOF-FLAG              PIC X(1) VALUE 'N'.
01  WS-ACCOUNT-TOTAL         PIC 9(10)V99 VALUE ZERO.
01  WS-CURRENT-ACCOUNT       PIC X(10) VALUE SPACES.
01  WS-CURRENT-DATE          PIC X(8) VALUE SPACES.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    * Merge daily files with OUTPUT PROCEDURE for account summarization
    SORT-MERGE SORT-MERGE-WORK
        ON ASCENDING KEY MERGE-DATE
        ON ASCENDING KEY MERGE-ACCOUNT
        USING DAILY-FILE-1, DAILY-FILE-2
        OUTPUT PROCEDURE GENERATE-ACCOUNT-SUMMARY
    
    DISPLAY "Sort-merge with output procedure completed"
    STOP RUN.
 
GENERATE-ACCOUNT-SUMMARY.
    OPEN OUTPUT SUMMARY-FILE
    PERFORM UNTIL WS-EOF-FLAG = 'Y'
        RETURN SORT-MERGE-WORK
            AT END MOVE 'Y' TO WS-EOF-FLAG
            NOT AT END
                * Check for account change
                IF MERGE-ACCOUNT NOT = WS-CURRENT-ACCOUNT
                    * Write account total if not first account
                    IF WS-CURRENT-ACCOUNT NOT = SPACES
                        MOVE WS-ACCOUNT-TOTAL TO SUMMARY-LINE(20:12)
                        MOVE "Account Total: " TO SUMMARY-LINE(1:15)
                        WRITE SUMMARY-RECORD
                    END-IF
                    * Start new account
                    MOVE MERGE-ACCOUNT TO WS-CURRENT-ACCOUNT
                    MOVE ZERO TO WS-ACCOUNT-TOTAL
                    MOVE "Account: " TO SUMMARY-LINE(1:9)
                    MOVE MERGE-ACCOUNT TO SUMMARY-LINE(10:10)
                    WRITE SUMMARY-RECORD
                END-IF
                * Add amount to account total
                ADD MERGE-AMOUNT TO WS-ACCOUNT-TOTAL
                * Write transaction record
                MOVE MERGE-DATE TO SUMMARY-LINE(1:8)
                MOVE MERGE-AMOUNT TO SUMMARY-LINE(20:12)
                MOVE MERGE-TRANSACTION-TYPE TO SUMMARY-LINE(35:1)
                WRITE SUMMARY-RECORD
        END-RETURN
    END-PERFORM
    * Write final account total
    IF WS-CURRENT-ACCOUNT NOT = SPACES
        MOVE WS-ACCOUNT-TOTAL TO SUMMARY-LINE(20:12)
        MOVE "Account Total: " TO SUMMARY-LINE(1:15)
        WRITE SUMMARY-RECORD
    END-IF
    CLOSE SUMMARY-FILE.

Explanation: This example demonstrates SORT-MERGE with an OUTPUT PROCEDURE that generates account summaries during the merge output phase. The GENERATE-ACCOUNT-SUMMARY procedure processes merged records and creates a summary report with account totals. It tracks account changes and accumulates transaction amounts, showing how OUTPUT PROCEDURE can be used for custom processing of merged data.

Monthly Consolidation Example

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* Monthly consolidation of daily transaction files
IDENTIFICATION DIVISION.
PROGRAM-ID. MONTHLY-CONSOLIDATION-EXAMPLE.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT DAILY-FILE-01 ASSIGN TO "DAILY01.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT DAILY-FILE-02 ASSIGN TO "DAILY02.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT DAILY-FILE-03 ASSIGN TO "DAILY03.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT DAILY-FILE-04 ASSIGN TO "DAILY04.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT DAILY-FILE-05 ASSIGN TO "DAILY05.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT MONTHLY-FILE ASSIGN TO "MONTHLY.DAT"
        ORGANIZATION IS SEQUENTIAL.
    SELECT SORT-MERGE-WORK ASSIGN TO "SORTWORK".
 
DATA DIVISION.
FILE SECTION.
SD  SORT-MERGE-WORK.
01  SORT-MERGE-RECORD.
    05  MERGE-TRANSACTION-DATE PIC X(8).
    05  MERGE-CUSTOMER-ID     PIC X(10).
    05  MERGE-PRODUCT-CODE    PIC X(5).
    05  MERGE-QUANTITY        PIC 9(5).
    05  MERGE-UNIT-PRICE      PIC 9(6)V99.
    05  MERGE-TOTAL-AMOUNT    PIC 9(8)V99.
 
FD  DAILY-FILE-01.
01  DAILY-01-RECORD.
    05  DAILY-01-DATE         PIC X(8).
    05  DAILY-01-CUSTOMER     PIC X(10).
    05  DAILY-01-PRODUCT      PIC X(5).
    05  DAILY-01-QTY          PIC 9(5).
    05  DAILY-01-PRICE        PIC 9(6)V99.
    05  DAILY-01-AMOUNT       PIC 9(8)V99.
 
FD  DAILY-FILE-02.
01  DAILY-02-RECORD.
    05  DAILY-02-DATE         PIC X(8).
    05  DAILY-02-CUSTOMER     PIC X(10).
    05  DAILY-02-PRODUCT      PIC X(5).
    05  DAILY-02-QTY          PIC 9(5).
    05  DAILY-02-PRICE        PIC 9(6)V99.
    05  DAILY-02-AMOUNT       PIC 9(8)V99.
 
FD  DAILY-FILE-03.
01  DAILY-03-RECORD.
    05  DAILY-03-DATE         PIC X(8).
    05  DAILY-03-CUSTOMER     PIC X(10).
    05  DAILY-03-PRODUCT      PIC X(5).
    05  DAILY-03-QTY          PIC 9(5).
    05  DAILY-03-PRICE        PIC 9(6)V99.
    05  DAILY-03-AMOUNT       PIC 9(8)V99.
 
FD  DAILY-FILE-04.
01  DAILY-04-RECORD.
    05  DAILY-04-DATE         PIC X(8).
    05  DAILY-04-CUSTOMER     PIC X(10).
    05  DAILY-04-PRODUCT      PIC X(5).
    05  DAILY-04-QTY          PIC 9(5).
    05  DAILY-04-PRICE        PIC 9(6)V99.
    05  DAILY-04-AMOUNT       PIC 9(8)V99.
 
FD  DAILY-FILE-05.
01  DAILY-05-RECORD.
    05  DAILY-05-DATE         PIC X(8).
    05  DAILY-05-CUSTOMER     PIC X(10).
    05  DAILY-05-PRODUCT      PIC X(5).
    05  DAILY-05-QTY          PIC 9(5).
    05  DAILY-05-PRICE        PIC 9(6)V99.
    05  DAILY-05-AMOUNT       PIC 9(8)V99.
 
FD  MONTHLY-FILE.
01  MONTHLY-RECORD.
    05  MONTHLY-DATE          PIC X(8).
    05  MONTHLY-CUSTOMER      PIC X(10).
    05  MONTHLY-PRODUCT       PIC X(5).
    05  MONTHLY-QTY           PIC 9(5).
    05  MONTHLY-PRICE         PIC 9(6)V99.
    05  MONTHLY-AMOUNT        PIC 9(8)V99.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    * Consolidate five daily files into monthly file
    SORT-MERGE SORT-MERGE-WORK
        ON ASCENDING KEY MERGE-TRANSACTION-DATE
        ON ASCENDING KEY MERGE-CUSTOMER-ID
        ON ASCENDING KEY MERGE-PRODUCT-CODE
        USING DAILY-FILE-01, DAILY-FILE-02, DAILY-FILE-03, 
              DAILY-FILE-04, DAILY-FILE-05
        GIVING MONTHLY-FILE
    
    DISPLAY "Monthly consolidation completed successfully"
    STOP RUN.

Explanation: This example demonstrates a practical application of SORT-MERGE for monthly consolidation of daily transaction files. The program merges five daily files (representing different days of the month) into a single monthly file. The merge is performed by transaction date, customer ID, and product code, creating a consolidated view of all transactions for the month in chronological order.

Best Practices and Considerations

Important Considerations

All input files must be sorted in the same order as merge keys
Define sort-merge files with SD statements in the FILE SECTION
Ensure sufficient disk space for sort-merge work files
Use appropriate merge keys for optimal performance
Consider using OUTPUT PROCEDURE for custom processing of merged data

Advantages

Efficient merging of pre-sorted files
Maintains sort order in output file
Supports multiple input files
Uses optimized merge algorithms
Provides OUTPUT PROCEDURE for custom processing

Limitations

Requires input files to be pre-sorted
Needs temporary disk space for work files
Limited to sequential file processing
Performance depends on disk I/O speed
Requires proper file definitions and error handling

Performance Tips

• Ensure all input files are properly sorted before merging
• Choose merge keys carefully to minimize processing complexity
• Use OUTPUT PROCEDURE for custom data processing during merge
• Monitor disk space for sort-merge work files
• Consider file sizes and merge performance characteristics

Test Your Knowledge

1. What is the primary purpose of the SORT-MERGE statement in COBOL?

To sort data in memory
To merge multiple sorted files into a single sorted output
To sort programs
To merge memory

2. In which COBOL division is the SORT-MERGE statement typically used?

IDENTIFICATION DIVISION
ENVIRONMENT DIVISION
DATA DIVISION
PROCEDURE DIVISION

3. What is the relationship between SORT-MERGE and SORT statements?

They are the same thing
SORT-MERGE combines sorted files, SORT sorts unsorted files
SORT-MERGE is faster than SORT
SORT-MERGE is obsolete, SORT is modern

4. Can SORT-MERGE be used with unsorted input files?

Yes, with any files
No, input files must be sorted
No, only with indexed files
Only with specific file types

5. What is the difference between SORT-MERGE and file concatenation?

They are the same thing
SORT-MERGE maintains sort order, concatenation does not
SORT-MERGE is faster than concatenation
SORT-MERGE is obsolete, concatenation is modern

COBOL Tutorial

COBOL SORT-MERGE Statement - Quick Reference

Primary Use

Division

File Type

Performance

Overview

Syntax

Practical Examples

Basic SORT-MERGE Operation

Multi-Key SORT-MERGE Operation

SORT-MERGE with OUTPUT PROCEDURE

Monthly Consolidation Example

Best Practices and Considerations

Important Considerations

Advantages

Limitations

Performance Tips

Test Your Knowledge

Related Concepts

SORT Statement

SD Statement

File Processing

Data Consolidation

External Sort Utility

Related Pages

COBOL Tutorial

COBOL SORT-MERGE Statement - Quick Reference

Primary Use

Division

File Type

Performance

Overview

Syntax

Practical Examples

Basic SORT-MERGE Operation

Multi-Key SORT-MERGE Operation

SORT-MERGE with OUTPUT PROCEDURE

Monthly Consolidation Example

Best Practices and Considerations

Important Considerations

Advantages

Limitations

Performance Tips

Test Your Knowledge

Frequently Asked Questions

Related Concepts

SORT Statement

SD Statement

File Processing

Data Consolidation

External Sort Utility

Related Pages