Event

Enhanced Definition

In the context of z/OS, an **event** is a significant occurrence, change in state, or condition within the system or an application that requires attention, logging, or a specific response. These occurrences can originate from hardware, software, or user actions, signaling a need for monitoring, intervention, or automated processing. In the context of IBM mainframe systems, an **event** is a significant occurrence or change in state within the hardware, operating system (z/OS), or an application that may require attention, trigger a response, or be recorded for analysis. Events can range from routine system operations to critical error conditions.

Key Characteristics

- Asynchronous Nature: Many events occur asynchronously, meaning they are not directly initiated by the currently executing program but rather by external factors, hardware interrupts, or other system processes.
- Trigger for Action: Events often serve as triggers for subsequent actions, such as writing messages to the operator console (WTO), generating SMF records, initiating automated recovery, or alerting system administrators.
- Source Identification: Events are typically associated with a specific source, such as a particular CPU, I/O device, address space, task, application (e.g., CICS, DB2), or system component.
- Time-Stamped and Logged: Critical events are almost always time-stamped and recorded in various system logs (e.g., SYSLOG, SMF records, application-specific logs) for historical analysis, auditing, and problem determination.
- Severity Levels: Events can have varying levels of severity, from informational messages to critical errors requiring immediate system operator intervention or automated shutdown procedures.
- Hardware vs. Software: Events can be hardware-generated (e.g., I/O errors, channel failures) or software-generated (e.g., program ABENDs, resource contention, security violations).

Use Cases

- System Monitoring and Alerting: An event could be a CPU utilization threshold being exceeded, a DASD volume running out of space, or a critical system component failing, triggering an alert to operations staff.
- Problem Determination: A program ABEND (abnormal end) is an event that generates diagnostic information (e.g., SVC dump, SYSOUT messages) used by developers and support staff to identify and resolve software defects.
- Security Auditing: Unauthorized access attempts, failed login attempts, or changes to critical system datasets are security events captured in SMF records and security logs for auditing and compliance.
- Workload Management: The completion of a JES job, the start of a CICS transaction, or a DB2 deadlock are events that the System Resource Manager (SRM) or workload managers might use to adjust resource allocation.
- Automated Operations: Events like a specific