Error handling is a crucial aspect of any programming language, including Control Language (CL). Proper error handling ensures that your programs can gracefully handle unexpected situations and provide meaningful feedback to users. In this section, we will cover the basics of error handling in CL, including common techniques and commands used to manage errors.

1. Error Messages: Understanding how CL communicates errors.
2. Monitoring for Errors: Techniques to detect and respond to errors.
3. Handling Errors: Strategies to manage errors when they occur.
4. Logging Errors: Keeping track of errors for debugging and auditing purposes.

In CL, error messages are generated when something goes wrong during the execution of a command or program. These messages provide information about what went wrong and can be used to diagnose and fix issues.

• CPF0001: The error code.
• Error occurred while processing command: The error description.

To handle errors effectively, you need to monitor for them. CL provides several commands and techniques to monitor for errors.

The MONMSG (Monitor Message) command is used to monitor for specific error messages and take action when they occur.

Syntax

• MSGID: The message ID to monitor.
• EXEC: The command to execute if the message is detected.

Example

In this example, if the error message CPF0001 is detected, the program sends a message indicating that an error occurred.

Once an error is detected, you need to decide how to handle it. Common strategies include:

1. Retrying the Operation: Attempting the operation again.
2. Logging the Error: Recording the error for later analysis.
3. Graceful Exit: Terminating the program in a controlled manner.

In this example, the program attempts an operation up to three times if the error CPF0001 occurs.

Logging errors is essential for debugging and auditing. You can use the SNDPGMMSG (Send Program Message) command to log errors.

In this example, if the error CPF0001 occurs, a message is sent to the system operator.

1. Write a CL program that performs a file operation (e.g., copying a file).
2. Use the MONMSG command to monitor for a specific error (e.g., CPF0001).
3. If the error occurs, log the error and retry the operation up to three times.
4. If the operation fails after three attempts, send a message indicating the failure.

Solution

In this section, we covered the basics of error handling in CL, including how to monitor for errors using the MONMSG command, strategies for handling errors, and logging errors for debugging and auditing purposes. Proper error handling is essential for creating robust and reliable CL programs. In the next section, we will explore subroutines and procedures to further enhance your CL programming skills.