Your COBOL application is encountering performance issues when reading large amounts of data from a VSAM file. What optimization techniques can you apply to improve performance?
- Apply caching mechanisms to reduce disk I/O
- Implement parallel processing for data retrieval
- Increase buffer size in COBOL I/O statements
- Use indexed file organization for faster access
To improve performance when reading large amounts of data from a VSAM file, applying caching mechanisms to reduce disk I/O is effective. Caching stores frequently accessed data in memory, minimizing the need for repeated disk reads and enhancing overall application speed.
When designing a modular COBOL application, you want to define a variable that will have scope across different programs but not be accessible from external applications. What approach would you choose?
- Declare the variable in the DATA DIVISION
- Use of copybooks
- Use of global variables
- Use of static variables
In COBOL, you can define a variable with scope across different programs by placing it in a copybook. Copybooks are reusable modules containing data definitions and are included in programs where the data is needed, ensuring data consistency and modularity while restricting access to external applications.
What is the primary purpose of the MOVE statement in COBOL?
- To control program flow
- To input data from the user
- To move data from one variable to another
- To perform arithmetic operations
The MOVE statement in COBOL is used to transfer data from one variable to another. It is essential for assigning values to variables and initializing data before processing.
You are working on a COBOL program that performs a merge operation on two sorted files. How can you ensure that the merge operation is efficient and optimized for performance?
- Implementing a binary search algorithm
- Pre-sorting the input files before merging
- Using indexed files for both input files
- Using the SORT verb provided by COBOL
Pre-sorting the input files before merging ensures that the records are already in sorted order, which simplifies the merge process and improves performance. This reduces the need for complex sorting algorithms during the merge operation.
In COBOL, what is the difference between the ADD and SUBTRACT statements when performing arithmetic operations?
- ADD adds values, and SUBTRACT subtracts values from the receiving field
- ADD and SUBTRACT are interchangeable in COBOL
- ADD is used for numeric addition, and SUBTRACT is used for alphanumeric subtraction
- ADD is used for subtraction, and SUBTRACT is used for addition
The ADD statement in COBOL is used for numeric addition, while the SUBTRACT statement is used for numeric subtraction. It's crucial to understand the distinction to perform accurate arithmetic operations in COBOL programs.
The "EVALUATE" statement can be used to simulate a _____ statement with multiple conditions.
- DIVIDE
- GOTO
- PERFORM
- Switch
The "EVALUATE" statement in COBOL serves a similar purpose as a "switch" statement in other programming languages. It allows for multiple conditions to be tested, providing a structured and efficient way to handle different cases.
In COBOL, the _____ clause is used to specify the action to be taken when a file operation results in an exception condition.
- ERROR HANDLING
- EXCEPTION HANDLER
- INVALID KEY
- ON EXCEPTION
In COBOL, the INVALID KEY clause is used to specify the action to be taken when a file operation results in an exception condition, such as attempting to read a record that does not exist.
In COBOL, what is the difference between the COMP and COMP-3 data types?
- COMP is a binary format, while COMP-3 is a packed decimal format
- COMP is the only numeric data type in COBOL
- COMP is used for characters, while COMP-3 is for numbers
- COMP-3 is an obsolete data type
The primary difference between COMP and COMP-3 in COBOL lies in their representation. COMP uses a binary format, while COMP-3 uses a packed decimal format, allowing for efficient storage of numeric data with a varying number of digits.
What is the purpose of the FUNCTION PRESENTATION intrinsic function in COBOL?
- It calculates the present value of an investment
- It converts a character string to a numeric value
- It retrieves the current presentation layer
- It returns the presentation of a numeric value as a character string
The FUNCTION PRESENTATION intrinsic function in COBOL is used to return the presentation of a numeric value as a character string, allowing for custom formatting.
In the context of COBOL file handling, what is "read-ahead" and how does it contribute to performance improvement?
- It reads multiple records in advance to reduce I/O wait time
- It reads records from the end of the file first
- It reads records sequentially for faster processing
- It skips unnecessary records during reading
"Read-ahead" in COBOL involves reading multiple records in advance and buffering them in memory, reducing I/O wait time and enhancing performance by minimizing the need for repeated disk access.
In COBOL, the _______ statement is used to perform a series of statements repeatedly.
- ITERATE
- LOOP
- PERFORM
- REPEAT
The PERFORM statement in COBOL is used to create loops, allowing a series of statements to be executed repeatedly. It provides various clauses for controlling the loop, such as UNTIL, WITH TEST BEFORE, and WITH TEST AFTER.
In a COBOL "IF" statement, what happens if the condition is not met?
- An error is generated
- The "ELSE" statement is executed
- The control transfers to the next statement outside the "IF" block
- The program terminates abruptly
If the condition in a COBOL "IF" statement is not met, the control transfers to the next statement outside the "IF" block. If an "ELSE" statement is present, it will be executed; otherwise, the program continues with the next statement.