Q: How do you implement file locking in COBOL programs?
A: To implement file locking in COBOL programs, we use the LOCK MODE clause in the SELECT statement. The LOCK MODE clause specifies the type of locking to be used for the file. For example, LOCK MODE IS EXCLUSIVE will lock the file exclusively, preventing other programs from accessing it.
Q: What is a record layout in COBOL, and how is it defined?
A: A record layout in
COBOL defines the structure and layout of a record in a file. It is defined using the FD (File Description) and 01 (Level Number) statements in the Data Division.
Q: How do you update a record in a file using COBOL?
A: To update a record in a file using COBOL, we use the UPDATE statement. The UPDATE statement updates the current record in the file with the data in the record area.
Q: What is a file status code, and how is it used in COBOL file handling?
A: A file status code is a numeric code that indicates the status of a file operation. It is used in COBOL file handling to detect and handle errors and exceptions.
Q: How do you delete a record from a file using COBOL?
A: To delete a record from a file using COBOL, we use the DELETE statement. The DELETE statement removes the current record from the file.
Q: What is a file organization in COBOL, and what are the different types?
A: A file organization in COBOL refers to the way data is stored in a file. The different types of file organization are sequential, indexed, and relative.
Q: What is the purpose of the ACCESS MODE clause in a COBOL SELECT statement?
A: The ACCESS MODE clause in a COBOL SELECT statement specifies the type of access to be used for the file. The different types are SEQUENTIAL, RANDOM, DYNAMIC, and EXTEND.
Q: How do you handle end-of-file conditions in COBOL file handling?
A: To handle end-of-file conditions in COBOL file handling, we use the END-OF-FILE phrase on the READ statement. This phrase is executed when there are no more records to be read from the file.
Q: What is the difference between a physical and a logical record in COBOL?
A: A physical record in COBOL is the actual record stored on disk, while a logical record is a record as it is represented in the program.
Q: How do you handle duplicate keys in an indexed file in COBOL?
A: To handle duplicate keys in an indexed file in COBOL, we use the DUPLICATES clause in the SELECT statement. This clause specifies how duplicate keys should be handled, such as by ignoring them or storing them in a separate file.
Q: What is the purpose of the FILE STATUS clause in COBOL file handling?
A: The FILE STATUS clause in COBOL file handling returns a status code that indicates the success or failure of a file operation. It is used to detect and handle errors and exceptions.
Q: What is a VSAM file in COBOL, and how is it different from a standard sequential file?
A: A VSAM file in
COBOL is a type of file that is used for high-performance data access. It is different from a standard sequential file because it allows for direct access to records using a key.
Q: How do you handle record locking in COBOL file handling?
A: To handle record locking in COBOL file handling, we use the LOCK and UNLOCK statements. The LOCK statement locks a record in the file, preventing other programs from accessing it, while the UNLOCK statement releases the lock.
Q: What is a relative record number in COBOL file handling, and how is it used?
A: A relative record number in COBOL file handling is a unique identifier that is assigned to each record in a relative file. It is used to access records directly using the RBA (Relative Byte Address) of the record.
Q: What is the difference between an OPEN INPUT and OPEN OUTPUT statement in COBOL file handling?
A: An OPEN INPUT statement in COBOL file handling opens a file for reading, while an OPEN OUTPUT statement opens a file for writing.
Q: How do you handle file sharing in COBOL file handling?
A: To handle file sharing in COBOL file handling, we use the SHARE OPTIONS clause in the SELECT statement. This clause specifies how the file should be shared among different programs.
Q: What is a blocking factor in COBOL file handling, and how is it used?
A: A blocking factor in COBOL file handling is the number of records that are read or written at one time. It is used to optimize file access by reducing the number of I/O operations.
Q: How do you handle errors and exceptions in COBOL file handling?
A: To handle errors and exceptions in COBOL file handling, we use the FILE STATUS clause and the various file status codes. We also use the INVALID KEY and AT END phrases on the READ statement to handle specific errors.
Q: What is the difference between a fixed-length record and a variable-length record in COBOL?
A: A fixed-length record in COBOL file handling has a set length, while a variable-length record can have a different length for each record. Variable-length records are often used for text files.
Q: What is a relative file in COBOL, and how is it different from an indexed file?
A: A relative file in COBOL is a type of file that is organized based on the record's position within the file. It is different from an indexed file because it does not use keys to access records.
Q: What is the purpose of the REWRITE statement in COBOL file handling?
A: The REWRITE statement in COBOL file handling updates the current record in the file with the data in the record area. It is used to modify an existing record without deleting and re-adding it to the file.
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