In this section, we will explore the essential concepts and techniques for logging and monitoring in Control Language (CL). Effective logging and monitoring are crucial for maintaining the health and performance of your systems, diagnosing issues, and ensuring smooth operations.

1. Logging:

   • Definition: The process of recording events, errors, and informational messages generated by a program.
   • Purpose: Helps in debugging, auditing, and understanding the behavior of the system.

2. Monitoring:

   • Definition: The continuous observation of a system's performance and health.
   • Purpose: Ensures the system is running optimally and helps in early detection of issues.

CL provides several commands to facilitate logging. Here are some of the most commonly used ones:

• SNDPGMMSG (Send Program Message): Sends a message to a program message queue.
• SNDMSG (Send Message): Sends a message to a user or a message queue.
• WRKMSG (Work with Messages): Displays messages in a message queue.

Explanation:

• DCL VAR(&MSG) TYPE(*CHAR) LEN(50): Declares a variable &MSG of type character with a length of 50.
• CHGVAR VAR(&MSG) VALUE('This is a log message.'): Changes the value of &MSG to the log message.
• SNDPGMMSG MSG(&MSG) TOUSR(*SYSOPR): Sends the message to the system operator's message queue.

Task: Write a CL program that logs a custom message to the system operator's message queue.

Solution:

• WRKSYSSTS (Work with System Status): Displays the current status of the system.
• WRKACTJOB (Work with Active Jobs): Displays a list of active jobs and their status.
• DSPLOG (Display Log): Displays the system log.

Explanation:

• WRKSYSSTS: This command displays the current system status, including CPU usage, memory usage, and other critical metrics.

Task: Write a CL program that displays the active jobs on the system.

Solution:

Message files can be used to store and manage messages more efficiently.

• CRTMSGF (Create Message File): Creates a message file.
• ADDMSGD (Add Message Description): Adds a message description to a message file.
• SNDPGMMSG (Send Program Message): Sends a message from a message file.

1. Create a Message File:

   CRTMSGF MSGF(MYLIB/MYMSGF) TEXT('My Message File')
   

2. Add a Message Description:

   ADDMSGD MSGID(MYMSG001) MSGF(MYLIB/MYMSGF) MSG('This is a message from the message file.')
   

3. Send a Message from the Message File:

   PGM
       SNDPGMMSG MSGID(MYMSG001) MSGF(MYLIB/MYMSGF) TOUSR(*SYSOPR)
   ENDPGM
   

Explanation:

• CRTMSGF MSGF(MYLIB/MYMSGF) TEXT('My Message File'): Creates a message file named MYMSGF in library MYLIB.
• ADDMSGD MSGID(MYMSG001) MSGF(MYLIB/MYMSGF) MSG('This is a message from the message file.'): Adds a message description with ID MYMSG001 to the message file.
• SNDPGMMSG MSGID(MYMSG001) MSGF(MYLIB/MYMSGF) TOUSR(*SYSOPR): Sends the message with ID MYMSG001 from the message file to the system operator's message queue.

In this section, we covered the basics of logging and monitoring in CL, including:

• Key concepts of logging and monitoring.
• Basic logging commands and practical examples.
• Basic monitoring commands and practical examples.
• Advanced techniques using message files.

By mastering these techniques, you can ensure that your CL programs are well-documented and that your system's performance and health are continuously monitored. This will help you quickly identify and resolve issues, leading to more reliable and efficient operations.