COBOL Tutorial

COBOL RELEASE Statement - Quick Reference

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Overview

The RELEASE statement is used in sort operations to write records to a sort work file. It is specifically designed to work within the INPUT PROCEDURE of a SORT statement, allowing you to process, filter, or transform records before they are sorted.

Purpose and Usage

Sort work file writing - Write records to sort work file
INPUT PROCEDURE support - Used within SORT INPUT PROCEDUREs
Record filtering - Select which records to include in sort
Data transformation - Modify records before sorting
Sort optimization - Control sort input processing

Sort Operation Flow

1. INPUT PROCEDURE executes

2. RELEASE statements write records to sort work file

3. SORT automatically sorts all released records

4. OUTPUT PROCEDURE processes sorted records

RELEASE → Sort Work File → SORT → Output

RELEASE is part of the sort process, not a standalone file operation.

Syntax

The RELEASE statement follows specific syntax patterns within SORT operations and INPUT PROCEDUREs.

Basic Syntax

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* Basic RELEASE statement syntax
RELEASE record-name
 
* With FROM clause
RELEASE record-name FROM data-name
 
* Complete SORT example with RELEASE
SORT SORT-WORK-FILE
    ON ASCENDING KEY SORT-KEY
    INPUT PROCEDURE IS INPUT-PROC
    OUTPUT PROCEDURE IS OUTPUT-PROC.
 
INPUT-PROC SECTION.
INPUT-PROCESS.
    OPEN INPUT INPUT-FILE
    PERFORM READ-AND-RELEASE UNTIL END-OF-FILE
    CLOSE INPUT-FILE.
 
READ-AND-RELEASE.
    READ INPUT-FILE
       AT END
          MOVE 'Y' TO EOF-FLAG
       NOT AT END
          RELEASE SORT-RECORD FROM INPUT-RECORD
    END-READ.

RELEASE is used within INPUT PROCEDUREs to write records to the sort work file.

RELEASE vs WRITE Comparison

Aspect	RELEASE	WRITE
Usage context	SORT INPUT PROCEDURE	File processing
Target file	Sort work file	Regular file
File management	Automatic	Manual
Record ordering	Sorted automatically	Program controlled
Error handling	FILE STATUS	FILE STATUS

Error Handling Syntax

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* RELEASE with error handling
RELEASE sort-record FROM input-record
    ON OVERFLOW
       DISPLAY "Sort work file overflow"
       PERFORM ERROR-HANDLING
    NOT ON OVERFLOW
       ADD 1 TO RECORD-COUNT
END-RELEASE
 
* Using FILE STATUS
SORT SORT-WORK-FILE
    ON ASCENDING KEY SORT-KEY
    INPUT PROCEDURE IS INPUT-PROC
    OUTPUT PROCEDURE IS OUTPUT-PROC
    FILE STATUS IS SORT-STATUS.
 
* Check status after RELEASE
RELEASE sort-record
IF SORT-STATUS NOT = "00"
   DISPLAY "RELEASE error: " SORT-STATUS
   PERFORM ERROR-HANDLING
END-IF

RELEASE supports error handling with ON OVERFLOW and FILE STATUS.

Practical Examples

These examples demonstrate how to use the RELEASE statement effectively in different sort scenarios.

Basic Sort with RELEASE

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IDENTIFICATION DIVISION.
PROGRAM-ID. BASIC-SORT.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT INPUT-FILE ASSIGN TO "INPUT.DAT"
        ORGANIZATION IS SEQUENTIAL
        FILE STATUS IS INPUT-STATUS.
        
    SELECT OUTPUT-FILE ASSIGN TO "OUTPUT.DAT"
        ORGANIZATION IS SEQUENTIAL
        FILE STATUS IS OUTPUT-STATUS.
 
DATA DIVISION.
FILE SECTION.
FD  INPUT-FILE.
01  INPUT-RECORD.
    05  INPUT-KEY        PIC 9(5).
    05  INPUT-DATA       PIC X(20).
 
SD  SORT-WORK-FILE.
01  SORT-RECORD.
    05  SORT-KEY         PIC 9(5).
    05  SORT-DATA        PIC X(20).
 
FD  OUTPUT-FILE.
01  OUTPUT-RECORD.
    05  OUTPUT-KEY       PIC 9(5).
    05  OUTPUT-DATA      PIC X(20).
 
WORKING-STORAGE SECTION.
01  FILE-STATUSES.
    05  INPUT-STATUS     PIC XX.
    05  OUTPUT-STATUS    PIC XX.
01  EOF-FLAG             PIC X VALUE 'N'.
    88  END-OF-FILE       VALUE 'Y'.
 
PROCEDURE DIVISION.
MAIN-PROCESS.
    SORT SORT-WORK-FILE
        ON ASCENDING KEY SORT-KEY
        INPUT PROCEDURE IS INPUT-PROC
        OUTPUT PROCEDURE IS OUTPUT-PROC
    STOP RUN.
 
INPUT-PROC SECTION.
INPUT-PROCESS.
    OPEN INPUT INPUT-FILE
    PERFORM READ-AND-RELEASE UNTIL END-OF-FILE
    CLOSE INPUT-FILE.
 
READ-AND-RELEASE.
    READ INPUT-FILE
       AT END
          MOVE 'Y' TO EOF-FLAG
       NOT AT END
          RELEASE SORT-RECORD FROM INPUT-RECORD
    END-READ.
 
OUTPUT-PROC SECTION.
OUTPUT-PROCESS.
    OPEN OUTPUT OUTPUT-FILE
    PERFORM READ-AND-WRITE UNTIL END-OF-FILE
    CLOSE OUTPUT-FILE.
 
READ-AND-WRITE.
    RETURN SORT-WORK-FILE
       AT END
          MOVE 'Y' TO EOF-FLAG
       NOT AT END
          WRITE OUTPUT-RECORD FROM SORT-RECORD
    END-RETURN.

This example shows a complete sort operation using RELEASE in the INPUT PROCEDURE.

Filtered Sort with RELEASE

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* Sort only records that meet certain criteria
INPUT-PROCESS.
    OPEN INPUT INPUT-FILE
    PERFORM READ-AND-FILTER UNTIL END-OF-FILE
    CLOSE INPUT-FILE.
 
READ-AND-FILTER.
    READ INPUT-FILE
       AT END
          MOVE 'Y' TO EOF-FLAG
       NOT AT END
          * Only RELEASE records that meet criteria
          IF INPUT-KEY > 1000 AND INPUT-KEY < 5000
             RELEASE SORT-RECORD FROM INPUT-RECORD
          END-IF
    END-READ.
 
* Sort with data transformation
READ-AND-TRANSFORM.
    READ INPUT-FILE
       AT END
          MOVE 'Y' TO EOF-FLAG
       NOT AT END
          * Transform data before sorting
          MOVE INPUT-KEY TO SORT-KEY
          MOVE FUNCTION UPPER-CASE(INPUT-DATA) TO SORT-DATA
          RELEASE SORT-RECORD
    END-READ.

RELEASE allows filtering and transformation of records before sorting.

Multi-Key Sort with RELEASE

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* Sort with multiple keys
SORT SORT-WORK-FILE
    ON ASCENDING KEY PRIMARY-KEY
    ON DESCENDING KEY SECONDARY-KEY
    INPUT PROCEDURE IS INPUT-PROC
    OUTPUT PROCEDURE IS OUTPUT-PROC.
 
* Data structure for multi-key sort
01  SORT-RECORD.
    05  PRIMARY-KEY      PIC 9(5).
    05  SECONDARY-KEY    PIC X(10).
    05  SORT-DATA        PIC X(20).
 
* RELEASE with multiple keys
READ-AND-RELEASE-MULTI.
    READ INPUT-FILE
       AT END
          MOVE 'Y' TO EOF-FLAG
       NOT AT END
          * Set up sort keys
          MOVE INPUT-DEPT TO PRIMARY-KEY
          MOVE INPUT-NAME TO SECONDARY-KEY
          MOVE INPUT-RECORD TO SORT-DATA
          RELEASE SORT-RECORD
    END-READ.

RELEASE supports complex sorting with multiple keys and different sort orders.

Performance Considerations

Understanding the performance implications of using RELEASE statements helps optimize sort operations.

Performance Impact Analysis

I/O operations - Each RELEASE requires a write to sort work file
Memory usage - Sort work file size affects memory requirements
Processing overhead - INPUT PROCEDURE adds processing time
Filtering efficiency - RELEASE can reduce sort data volume
Sort algorithm impact - Reduced data improves sort performance

Optimization Strategies

Strategy	Benefit	Implementation
Early filtering	Reduce sort data volume	Use IF conditions before RELEASE
Data transformation	Optimize sort keys	Transform data before RELEASE
Batch processing	Reduce I/O overhead	Process multiple records together
Memory optimization	Improve sort performance	Use appropriate sort work file size
Key optimization	Faster sorting	Use efficient key structures

When to Use RELEASE vs Direct Sort

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* Use RELEASE when you need filtering/transformation
SORT SORT-WORK-FILE
    ON ASCENDING KEY SORT-KEY
    INPUT PROCEDURE IS INPUT-PROC    * Use when filtering needed
    OUTPUT PROCEDURE IS OUTPUT-PROC.
 
* Use direct sort when processing all records
SORT SORT-WORK-FILE
    ON ASCENDING KEY SORT-KEY
    USING INPUT-FILE                 * Direct sort - no filtering
    GIVING OUTPUT-FILE.
 
* RELEASE is beneficial when:
* - Only some records need sorting
* - Data transformation is required
* - Complex filtering logic is needed
* - Multiple input files need merging

Choose between RELEASE and direct sort based on your processing requirements.

Best Practices and Tips

Following these best practices ensures effective use of the RELEASE statement in sort operations.

RELEASE Best Practices

Use for filtering - RELEASE when you need to filter records
Transform data early - Do transformations before RELEASE
Handle errors properly - Check FILE STATUS after RELEASE
Optimize sort keys - Use efficient key structures
Document INPUT PROCEDUREs - Clearly document filtering logic
Test with large datasets - Verify performance with realistic data

Common Pitfalls to Avoid

Pitfall	Problem	Solution
Using RELEASE outside SORT	Compilation error	Only use in INPUT PROCEDUREs
Ignoring error handling	Silent failures	Check FILE STATUS
Inefficient filtering	Poor performance	Filter before RELEASE
Memory issues	Sort work file overflow	Monitor sort work file size
Complex transformations	Slow processing	Keep transformations simple

Error Handling Best Practices

Check FILE STATUS - Monitor for RELEASE errors
Use ON OVERFLOW - Handle sort work file overflow
Log errors - Record error conditions for debugging
Provide recovery - Implement error recovery procedures
Validate data - Check data before RELEASE
Monitor performance - Track sort operation performance

RELEASE Statement Quick Reference

Usage	Syntax	Example
Basic RELEASE	RELEASE record-name	RELEASE SORT-RECORD
With FROM clause	RELEASE record-name FROM data-name	RELEASE SORT-RECORD FROM INPUT-RECORD
With error handling	RELEASE record-name ON OVERFLOW	RELEASE SORT-RECORD ON OVERFLOW
In INPUT PROCEDURE	INPUT PROCEDURE IS proc-name	INPUT PROCEDURE IS INPUT-PROC
With filtering	IF condition RELEASE record-name	IF KEY > 1000 RELEASE SORT-RECORD

Test Your Knowledge

1. What is the primary purpose of the RELEASE statement in COBOL?

To free memory
To write records to a sort work file
To close files
To delete records

2. In which context is the RELEASE statement most commonly used?

File processing
Sort operations
Memory management
Screen handling

3. What happens when a RELEASE statement is executed?

A record is written to the sort work file
Memory is freed
A file is closed
A record is deleted

4. What is the relationship between RELEASE and SORT statements?

They are the same thing
RELEASE is used within SORT operations
SORT is used within RELEASE operations
They are unrelated

5. Which of the following is a valid RELEASE statement syntax?

RELEASE record-name
RELEASE FROM data-name
RELEASE record-name FROM data-name
All of the above

Frequently Asked Questions

Related Concepts

SORT Statement

Understanding the SORT statement for data sorting operations.

RETURN Statement

Using RETURN to read sorted records from sort work file.

Sort-Merge Operations

Complete guide to sort and merge operations in COBOL.

File Processing

Understanding file processing operations in COBOL.

Error Handling

Handling errors in COBOL programs.

REFERENCE Clause REMAINDER Clause

COBOL Tutorial

COBOL RELEASE Statement - Quick Reference

Overview

Purpose and Usage

Sort Operation Flow

Syntax

Basic Syntax

RELEASE vs WRITE Comparison

Error Handling Syntax

Practical Examples

Basic Sort with RELEASE

Filtered Sort with RELEASE

Multi-Key Sort with RELEASE

Performance Considerations

Performance Impact Analysis

Optimization Strategies

When to Use RELEASE vs Direct Sort

Best Practices and Tips

RELEASE Best Practices

Common Pitfalls to Avoid

Error Handling Best Practices

RELEASE Statement Quick Reference

Test Your Knowledge

Frequently Asked Questions

What is the difference between RELEASE and WRITE statements in COBOL?

How does the RELEASE statement work in the context of a SORT operation?

Can you use RELEASE without a SORT statement?

What are the performance implications of using RELEASE in sort operations?

How do you handle errors when using the RELEASE statement?

Related Concepts

SORT Statement

RETURN Statement

Sort-Merge Operations

File Processing

Error Handling

Related Pages