MainframeMaster

COBOL Tutorial

COBOL SD Statement - Quick Reference

Progress0 of 0 lessons

Overview

The SD statement is used to define sort-merge files in COBOL. These files are used as temporary storage during SORT and MERGE operations and are managed automatically by the SORT utility.

Purpose and Usage

  • Sort-merge files - Define temporary files for sorting operations
  • SORT utility - Work with the COBOL SORT utility
  • Temporary storage - Provide temporary storage during sorting
  • Large datasets - Handle datasets too large for memory sorting
  • Automatic management - Files managed by SORT utility

Syntax

The SD statement follows a simple syntax for defining sort-merge files.

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
35
36
37
* Basic SD statement syntax
SD  sort-file-name.
01  record-name.
    * record description
 
* Complete example
IDENTIFICATION DIVISION.
PROGRAM-ID. SORT-EXAMPLE.
 
DATA DIVISION.
FILE SECTION.
SD  SORT-WORK-FILE.
01  SORT-RECORD.
    05  SORT-KEY-1    PIC X(10).
    05  SORT-KEY-2    PIC 9(6).
    05  SORT-DATA     PIC X(50).
 
FD  INPUT-FILE.
01  INPUT-RECORD.
    05  INPUT-KEY-1   PIC X(10).
    05  INPUT-KEY-2   PIC 9(6).
    05  INPUT-DATA    PIC X(50).
 
FD  OUTPUT-FILE.
01  OUTPUT-RECORD.
    05  OUTPUT-KEY-1  PIC X(10).
    05  OUTPUT-KEY-2  PIC 9(6).
    05  OUTPUT-DATA   PIC X(50).
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    SORT SORT-WORK-FILE
        ON ASCENDING KEY SORT-KEY-1
        ON DESCENDING KEY SORT-KEY-2
        USING INPUT-FILE
        GIVING OUTPUT-FILE
    STOP RUN.

SD defines the structure for sort-merge operations.

Practical Examples

Examples of using the SD statement in different sorting scenarios.

Simple Sort Operation

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
* Simple sort with SD
DATA DIVISION.
FILE SECTION.
SD  SORT-FILE.
01  SORT-RECORD.
    05  SORT-KEY      PIC X(20).
    05  SORT-VALUE    PIC 9(6).
 
FD  UNSORTED-FILE.
01  UNSORTED-RECORD.
    05  UNSORTED-KEY  PIC X(20).
    05  UNSORTED-VALUE PIC 9(6).
 
FD  SORTED-FILE.
01  SORTED-RECORD.
    05  SORTED-KEY    PIC X(20).
    05  SORTED-VALUE  PIC 9(6).
 
PROCEDURE DIVISION.
SORT-DATA.
    SORT SORT-FILE
        ON ASCENDING KEY SORT-KEY
        USING UNSORTED-FILE
        GIVING SORTED-FILE
    STOP RUN.

SD enables simple sorting operations.

Best Practices

Understanding best practices ensures effective use of the SD statement.

Best Practices

  • Match record structures - Ensure SD record matches input/output records
  • Use meaningful names - Choose descriptive file names
  • Plan sort keys - Design sort keys carefully
  • Consider performance - Use SD for large datasets
  • Test thoroughly - Verify sort operations work correctly

Test Your Knowledge

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

  • To define database files
  • To define sort-merge files
  • To define input files
  • To define output files

2. In which COBOL division is the SD statement typically used?

  • IDENTIFICATION DIVISION
  • ENVIRONMENT DIVISION
  • DATA DIVISION
  • PROCEDURE DIVISION

3. What does SD stand for in COBOL?

  • Sort Data
  • Sort Description
  • System Data
  • Storage Definition

4. Can SD files be used for regular file operations?

  • Yes, always
  • No, never
  • Only for reading
  • Only for writing

5. What is the relationship between SD and SORT statements?

  • They are the same thing
  • SD defines the file, SORT uses it
  • SD is faster than SORT
  • They cannot be used together

Frequently Asked Questions

Related Concepts

SORT Statement

Using SORT for data sorting operations.

File Processing

Understanding file processing in COBOL.

Data Division

Understanding the DATA DIVISION structure.

SCROLL ClauseSEARCH Statement