In the world of COBOL, file matching is one of the most common tasks. This process involves comparing two sequential files to find matching records. This tutorial will guide you through the various techniques and examples of file matching in COBOL. Here is the agenda for this article:
- Introduction.
- What is file matching logic in COBOL?
- COBOL File Matching logic flow diagram.
- COBOL File matching logic example.
- Tips and tricks.
- Conclusion.
Introduction to COBOL.
Common Business-Oriented Language (COBOL) is a highly influential high-level programming language that finds widespread use across diverse industries, including finance, administration, banking, retail, aviation, and more. Renowned for its exceptional file-handling capabilities, COBOL is a preferred choice for developing enterprise-level applications. With a long and storied history spanning several decades, COBOL is a robust programming language that continues to evolve and thrive.
What is File Matching in COBOL?
File matching in COBOL is a technique used to compare two or more sequential files. This process is often used to merge files based on a key or to identify matching records between files. The key to successful file matching in COBOL is understanding the logic behind the process.
COBOL File Matching Technique:
There are several techniques for file matching in COBOL. The most common method is to compare two sequential files. It involves reading records from both files simultaneously and comparing the key fields. If the keys match, the records are considered a match.
Another technique is to merge files based on a key. It involves sorting the files by the key field and combining them into one file. When working with massive datasets, this method is incredibly beneficial.
Here is the basic flow diagram that showcases how file-matching logic is implemented in COBOL programs.
Implementing file-matching logic in COBOL.
The main idea behind file matching in
COBOL is to compare records from one file with those from another based on specific criteria, typically key fields. To implement file-matching logic in COBOL, it is common to sort and merge files based on key fields and then compare corresponding records to identify similarities or differences.
To ensure efficient processing and accurate matching, files are often sorted in either ascending or descending order before comparing records.
Handling Different Scenarios.
File matching in COBOL can handle various scenarios, including one-to-one, one-to-many, and many-to-many matching, each requiring different approaches and algorithms.
- One-to-One Matching: In one-to-one matching, each record in one file corresponds to exactly one record in another, simplifying the matching process.
- One-to-Many Matching: One-to-many matching involves one record in one file corresponding to multiple records in another, requiring careful handling to avoid duplicate matches.
- Many-to-Many Matching: Many-to-many matching is the most complex scenario, where multiple records in one file correspond to multiple records in another file, necessitating sophisticated algorithms for accurate matching.
COBOL File Matching Logic Example:
Here is a sample COBOL program that explains the step-by-step process of file matching in COBOL. Please note this is not the complete program. It’s a basic example of file-matching logic in COBOL, and It highlights the core file-matching logic.
000100 IDENTIFICATION DIVISION.
000600*
002800 ENVIRONMENT DIVISION.
003900*
... ....
... ....
... ....
... ....
004000 DATA DIVISION.
004100 FILE SECTION.
004200 FD EMP-LIST.
004300 01 EMP-LIST-REC.
004400 05 EMPL-PCDE PIC X(01).
004500 05 FILLER PIC X(01).
004600 05 EMPL-EMPNO PIC 9(06).
004700 05 FILLER PIC X(72).
004800*
004900 FD EMP-FILE.
005000 COPY EMPRECC REPLACING ==(EP)== BY ==IN==.
005100*
005200 FD REP-FILE.
005300 01 REP-FILE-REC PIC X(150).
005400*
005500 WORKING-STORAGE SECTION.
005600*
018200*
018300 PROCEDURE DIVISION.
018400 0000-CORE-BUSINESS-LOGIC.
018500 PERFORM A000-INIT-VALS
018600 PERFORM B000-OPEN-FILE
018700 PERFORM C000-PRNT-HDRS
018800 PERFORM E000-READ-LIST-FILE
018900 PERFORM F000-READ-EMPLY-FILE
019000 PERFORM D000-PROCESS-RECDS
019100 PERFORM X000-CLSE-FILE
019200 STOP RUN.
019300*
019400 A000-INIT-VALS SECTION.
019500 A010-INIT-TMP-VALS.
019600 INITIALIZE WS-COUNTERS, DTL-LINE, TRL-LINE,
019700 WS-TEMP-DATE.
019800*
019900 A099-EXIT.
020000 EXIT.
020100*
020200 B000-OPEN-FILE SECTION.
020300 B010-OPEN-FILE.
020400 OPEN INPUT EMP-LIST, EMP-FILE
020500 OUTPUT REP-FILE.
020600 B099-EXIT.
020700 EXIT.
020800*
022500*
022500*
022500* FILE MATCHING LOGIC IN COBOL PROGRAM.
022500*
21000 D000-PROCESS-RECDS SECTION.
022700 D010-PROCESS-RECDS.
022800 PERFORM UNTIL END-OF-FILE
022900 EVALUATE TRUE
023000 WHEN EMPL-EMPNO > IN-EMPNO
023100 PERFORM F000-READ-EMPLY-FILE
023200 WHEN EMPL-EMPNO < IN-EMPNO
023300 PERFORM E000-READ-LIST-FILE
023400 WHEN EMPL-EMPNO = IN-EMPNO
023500 IF EMPL-PCDE = 'P'
023600 PERFORM G000-PRNT-REPT
023700 END-IF
023800 PERFORM E000-READ-LIST-FILE
023900 PERFORM F000-READ-EMPLY-FILE
024000 WHEN OTHER
024100 CONTINUE
024200 END-EVALUATE
024300 END-PERFORM.
024400*
024500 D099-EXIT.
024600 EXIT.
024700
024800 E000-READ-LIST-FILE SECTION.
024900 E010-READ-LIST-FILE.
025000 READ EMP-LIST
025100 AT END SET END-OF-FILE TO TRUE
025200 NOT AT END ADD +1 TO WS-INP-REC
025300 END-READ.
025400*
025500 E099-EXIT.
025600 EXIT.
025700*
025800 F000-READ-EMPLY-FILE SECTION.
025900 F010-READ-EMPLY-FILE.
026000 READ EMP-FILE
026100 AT END SET END-OF-FILE TO TRUE
026200 DISPLAY 'RECORD NOT FOUND ', EMPL-EMPNO
026300 END-READ.
026400*
026500 F099-EXIT.
026600 EXIT.
026700*
... ....
032000*
032100 X020-PRINT-TOTALS.
032200 DISPLAY '****** PROGRAM SUMMARY ****************'
032300 DISPLAY 'PGM EXECUTION DATE :', HD-DTE
032400 DISPLAY 'TOTAL NO OF RECORD READ :', WS-INP-REC
032500 DISPLAY 'TOTAL NO OF RECORD PRINT :', WS-OUT-REC
032600 DISPLAY '****************************************'.
032700*
032800 X099-EXIT.
032900 EXIT.
033000
In summary, this COBOL snippet reads records from two files (EMPLY-FILE and LIST-FILE), compares employee numbers, and performs different actions based on the comparison results.
Tips & Tricks.
Here are some tips and tricks for implementing file matching in COBOL:
- Always ensure that the matched files are sorted in the order of the key field.
- Use appropriate file-handling verbs like READ, WRITE, REWRITE, and DELETE as required.
- Handle exceptions using appropriate condition-handling statements.
YouTube Tutorial: COBOL File Matching Logic.
Interview Questions and Answers.
Q: Is COBOL still relevant in today's programming landscape?
A: Despite its age, COBOL remains relevant in many industries due to its robustness and reliability, especially in handling large-scale data processing tasks.
Q: What are some common challenges when implementing file-matching logic in COBOL?
A: Common challenges include performance optimization, error handling, handling large datasets efficiently, and integrating with modern systems.
Q: What role does file organization play in file-matching logic?
A: File organization dictates how records are stored and accessed, influencing the efficiency and effectiveness of file-matching algorithms in COBOL.
Q: Are there any modern alternatives to COBOL for file-matching tasks?
A: While newer languages and technologies are available, COBOL remains a preferred choice for file matching in industries where legacy systems and data compatibility are critical.
Q: How do I handle unmatched records?
A: You can write them to a separate file, flag them for review, or take other actions based on your requirements.
Q: Can I match files with different record structures?
A: Yes, but you may need to reformat or map fields before comparison.
Q: What are performance considerations for large files?
A: Consider indexed files or sorting techniques for optimization.
Best Practices
Conclusion.
Master file matching in COBOL with this essential guide. Discover the importance of file comparison for tasks like data synchronization and transaction processing. Learn the fundamentals of COBOL file matching logic, including working with sequential files, match keys, and handling unmatched records. Get practical tips and insights for optimizing your COBOL file-matching code.
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