COBOL Tutorial

COBOL GET Clause - Quick Reference

Progress0 of 0 lessons

Overview

The GET clause is used in COBOL to retrieve data from various sources including files, databases, external systems, and other data repositories. It provides a standardized way to access and retrieve information in COBOL programs.

Purpose and Usage

Data retrieval - Retrieve data from various sources
File operations - Read records from files
Database access - Retrieve data from databases
External systems - Access data from APIs and external systems
Standardized interface - Consistent data access method

Data Retrieval Flow

Source: [File] [Database] [API] [External System]

GET Operation: [Specify Source] → [Retrieve Data] → [Handle Result]

Error Handling: [INVALID KEY] [ON EXCEPTION] [Status Check]

GET provides unified data access interface

GET operations follow a consistent pattern regardless of data source.

Syntax

The GET clause follows specific syntax patterns for different types of data retrieval.

Basic Syntax

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
* Basic GET clause syntax
GET file-name [INVALID KEY imperative-statement]
    [NOT INVALID KEY imperative-statement]
    [END-GET]
 
GET data-name FROM source
    [ON EXCEPTION imperative-statement]
    [NOT ON EXCEPTION imperative-statement]
    [END-GET]
 
* Examples
GET CUSTOMER-FILE
    INVALID KEY
        DISPLAY 'Error reading file'
        STOP RUN
    END-GET
 
GET CUSTOMER-DATA FROM DATABASE-TABLE
    ON EXCEPTION
        DISPLAY 'Database error'
        PERFORM ERROR-HANDLING
    NOT ON EXCEPTION
        DISPLAY 'Data retrieved successfully'
    END-GET
 
* Complete example
GET API-RESPONSE FROM WEB-SERVICE
    ON EXCEPTION
        MOVE 'ERROR' TO STATUS-CODE
        PERFORM LOG-ERROR
    NOT ON EXCEPTION
        MOVE 'SUCCESS' TO STATUS-CODE
        PERFORM PROCESS-RESPONSE
    END-GET

GET can be used for file operations and external data retrieval.

Error Handling Options

Clause	Purpose	Use Case
INVALID KEY	Handle file access errors	File operations
ON EXCEPTION	Handle general exceptions	External systems
NOT INVALID KEY	Handle successful file operations	File operations
NOT ON EXCEPTION	Handle successful external operations	External systems

Data Source Types

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
* Different data source types for GET
* File operations
GET CUSTOMER-FILE
    INVALID KEY PERFORM ERROR-HANDLING
END-GET
 
* Database operations
GET CUSTOMER-RECORD FROM CUSTOMER-TABLE
    WHERE CUSTOMER-ID = 'CUST001'
    ON EXCEPTION PERFORM DB-ERROR-HANDLING
END-GET
 
* API operations
GET API-RESPONSE FROM REST-API
    USING 'https://api.example.com/data'
    ON EXCEPTION PERFORM API-ERROR-HANDLING
END-GET
 
* External system operations
GET SYSTEM-DATA FROM LEGACY-SYSTEM
    USING CONNECTION-PARAMETERS
    ON EXCEPTION PERFORM SYSTEM-ERROR-HANDLING
END-GET

GET supports various data source types with appropriate error handling.

Common Use Cases

GET is commonly used in specific scenarios where data retrieval from various sources is needed.

File Record Retrieval

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
* Retrieve records from sequential, indexed, or relative files
IDENTIFICATION DIVISION.
PROGRAM-ID. FILE-READER.
 
ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT CUSTOMER-FILE ASSIGN TO 'CUSTOMER.DAT'
        ORGANIZATION IS SEQUENTIAL
        ACCESS MODE IS SEQUENTIAL.
 
DATA DIVISION.
FILE SECTION.
FD  CUSTOMER-FILE.
01  CUSTOMER-RECORD.
    05  CUSTOMER-ID       PIC X(10).
    05  CUSTOMER-NAME     PIC X(50).
    05  CUSTOMER-ADDRESS  PIC X(100).
 
PROCEDURE DIVISION.
    OPEN INPUT CUSTOMER-FILE
    PERFORM UNTIL EOF
        GET CUSTOMER-FILE
            INVALID KEY
                DISPLAY 'Error reading file'
                STOP RUN
        END-GET
        DISPLAY 'Customer: ' CUSTOMER-NAME
    END-PERFORM
    CLOSE CUSTOMER-FILE
    STOP RUN.

GET is used to retrieve records from various file types.

Database Record Access

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
* Retrieve records from database tables
IDENTIFICATION DIVISION.
PROGRAM-ID. DB-READER.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  DB-CONNECTION.
    05  DB-NAME           PIC X(20) VALUE 'CUSTOMERDB'.
    05  DB-USER           PIC X(20) VALUE 'ADMIN'.
    05  DB-PASSWORD       PIC X(20) VALUE 'SECRET'.
 
01  CUSTOMER-DATA.
    05  CUST-ID           PIC X(10).
    05  CUST-NAME         PIC X(50).
    05  CUST-BALANCE      PIC 9(8)V99.
 
PROCEDURE DIVISION.
    CONNECT TO DATABASE DB-CONNECTION
    GET CUSTOMER-DATA FROM CUSTOMER-TABLE
        WHERE CUST-ID = 'CUST001'
        ON EXCEPTION
            DISPLAY 'Database error occurred'
            PERFORM ERROR-HANDLING
        NOT ON EXCEPTION
            DISPLAY 'Customer: ' CUST-NAME
            DISPLAY 'Balance: ' CUST-BALANCE
    END-GET
    DISCONNECT FROM DATABASE
    STOP RUN.

GET enables database record retrieval with error handling.

External System Data Retrieval

cobol

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
* Retrieve data from external systems, APIs, or web services
IDENTIFICATION DIVISION.
PROGRAM-ID. API-READER.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  API-ENDPOINT.
    05  API-URL           PIC X(100) VALUE 'https://api.example.com/data'.
    05  API-METHOD        PIC X(10) VALUE 'GET'.
    05  API-HEADERS       PIC X(200).
 
01  RESPONSE-DATA.
    05  STATUS-CODE       PIC 9(3).
    05  RESPONSE-BODY     PIC X(1000).
 
PROCEDURE DIVISION.
    SET API-HEADERS TO 'Content-Type: application/json'
    GET RESPONSE-DATA FROM API-ENDPOINT
        ON EXCEPTION
            DISPLAY 'API call failed'
            PERFORM ERROR-HANDLING
        NOT ON EXCEPTION
            IF STATUS-CODE = 200
                DISPLAY 'Data retrieved successfully'
                PERFORM PROCESS-RESPONSE
            ELSE
                DISPLAY 'API returned error: ' STATUS-CODE
            END-IF
    END-GET
    STOP RUN.

GET provides access to external systems and APIs.

Best Practices and Tips

Following these best practices ensures effective use of the GET clause for data retrieval operations.

GET Design Principles

Always handle errors - Use INVALID KEY or ON EXCEPTION clauses
Validate retrieved data - Check data integrity after retrieval
Close connections properly - Ensure proper cleanup of resources
Use meaningful variable names - Clear naming for better readability
Consider performance implications - Optimize for large datasets
Implement proper logging - Log operations for debugging

Common Pitfalls to Avoid

Pitfall	Problem	Solution
No error handling	Program crashes on errors	Always use INVALID KEY or ON EXCEPTION
Unclosed connections	Resource leaks and system issues	Properly close all connections
No data validation	Incorrect data processing	Validate retrieved data
Poor performance	Slow data retrieval	Optimize queries and use indexing
No logging	Difficult debugging	Implement comprehensive logging

Performance Considerations

Use indexed access - For large files to improve retrieval speed
Consider buffering strategies - For frequently accessed data
Minimize network calls - When accessing external systems
Use appropriate data types - To reduce memory usage
Consider caching mechanisms - For repeated data access
Monitor and optimize - Database query performance

When to Use GET

Use Case	GET Suitability	Reasoning
File data retrieval	Excellent	Natural fit for file operations
Database access	Excellent	Efficient for database operations
External system access	Good	Provides standardized interface
Simple data access	Good	Straightforward for basic operations
Complex data processing	Poor	Use specialized processing tools

GET Clause Quick Reference

Usage	Syntax	Example
File retrieval	GET file-name [INVALID KEY]	GET CUSTOMER-FILE INVALID KEY PERFORM ERROR
Database retrieval	GET data-name FROM source	GET CUSTOMER-DATA FROM CUSTOMER-TABLE
External system	GET data-name FROM source [ON EXCEPTION]	GET API-RESPONSE FROM WEB-SERVICE ON EXCEPTION
Error handling	[INVALID KEY] or [ON EXCEPTION]	INVALID KEY PERFORM ERROR-HANDLING
Success handling	[NOT INVALID KEY] or [NOT ON EXCEPTION]	NOT ON EXCEPTION PERFORM SUCCESS-HANDLING

Test Your Knowledge

1. What is the primary purpose of the GET clause in COBOL?

To write data to files
To retrieve data from various sources
To perform calculations
To control program flow

2. Which clause is used to handle file access errors in GET operations?

ON EXCEPTION
INVALID KEY
ERROR HANDLING
EXCEPTION HANDLER

3. What is the correct syntax for retrieving data from an external source?

GET data-name FROM source
RETRIEVE data-name FROM source
READ data-name FROM source
FETCH data-name FROM source

4. Which clause handles exceptions when retrieving data from external sources?

INVALID KEY
ON EXCEPTION
ERROR HANDLING
EXCEPTION HANDLER

5. What is the relationship between GET and READ in COBOL?

They are the same thing
GET is more general-purpose than READ
READ is more general-purpose than GET
They cannot be used together

Frequently Asked Questions

Related Concepts

READ Statement

Understanding the READ statement for file operations.

FILE-CONTROL

Understanding file control and file organization.

OPEN Statement

Understanding file opening operations.

CLOSE Statement

Understanding file closing operations.

Database Operations

Understanding database operations in COBOL.

FUNCTION-ID Clause IMPLEMENTS Clause

COBOL Tutorial

COBOL GET Clause - Quick Reference

Overview

Purpose and Usage

Data Retrieval Flow

Syntax

Basic Syntax

Error Handling Options

Data Source Types

Common Use Cases

File Record Retrieval

Database Record Access

External System Data Retrieval

Best Practices and Tips

GET Design Principles

Common Pitfalls to Avoid

Performance Considerations

When to Use GET

GET Clause Quick Reference

Test Your Knowledge

Frequently Asked Questions

What is the difference between GET and READ in COBOL?

Can GET be used with indexed files?

How do you handle end-of-file conditions with GET?

Can GET retrieve multiple records at once?

Is GET supported in all COBOL dialects?

Related Concepts

READ Statement

FILE-CONTROL

OPEN Statement

CLOSE Statement

Database Operations

Related Pages