Disarm - Deactivate

Enhanced Definition

In z/OS, "disarm" or "deactivate" refers to the controlled process of making a system component, resource, or function inactive, non-operational, or non-dispatchable. This action is typically performed to prevent its execution, release system resources, or prepare for maintenance, updates, or removal, ensuring a graceful cessation of activity.

Key Characteristics

- Controlled Cessation: It is a deliberate and often procedural action, requiring specific commands or system calls rather than an abrupt termination.
- Resource Management: Deactivating a component can free up associated system resources, such as memory, CPU cycles, or I/O paths.
- Prevents Execution: Stops a program, task, address space, or system function from being initiated or continuing its operations.
- Prerequisite for Change: Often a necessary step before applying system maintenance, configuration changes, software upgrades, or hardware modifications.
- Reversible State: Typically, a disarmed or deactivated component can be "armed" or "activated" again to restore its operational status.
- System Integrity: Performed to maintain the stability, consistency, and data integrity of the z/OS system during changes or problem resolution.

Use Cases

- Deactivating a CICS region: Before applying maintenance (e.g., PTFs) or configuration changes to a CICS address space, it might be deactivated to ensure no transactions are running.
- Disarming a specific trace facility: To temporarily stop the collection of trace data (e.g., GTF, SLIP traps) to save CPU cycles and storage, or to reconfigure the trace.
- Deactivating a System Logger log stream: To perform maintenance on the log stream dataset, its associated DASD, or to change its definition.
- Taking a DB2 subsystem offline: To apply maintenance, perform a full backup, or migrate the DB2 catalog/directory.
- Removing a JES initiator: To reduce the number of jobs that can be started concurrently, or to reconfigure JES parameters for that initiator.

Related Concepts

Disarming or deactivating is a fundamental aspect of system management and change control in z/OS. It is often a precursor to other activities like maintenance, upgrades, reconfigurations, or even a controlled IPL. It contrasts with termination or cancellation, which can be more abrupt and potentially disruptive. The concept is closely linked to system availability and resilience, as it enables controlled downtime for specific components while minimizing impact on the overall system. The opposite action, arming or activating, brings a component back into an operational state.

Best Practices:

Plan and Schedule: Always plan disarm/deactivate actions during scheduled maintenance windows to minimize impact on users and applications.
Notify Stakeholders: Inform application owners, users, and dependent system administrators well in advance of deactivating critical components.
Verify Dependencies: Before deactivation, thoroughly check for active processes, applications, or other system components that rely on the target component.
Document Procedures: Follow established and documented procedures for specific components to ensure proper deactivation and a smooth subsequent reactivation.
Monitor System Status: Continuously monitor the z/OS system and the status of the affected component before, during, and after the deactivation process.
Utilize Automation: Leverage z/OS automation tools like SA z/OS (System Automation for z/OS) to ensure consistent, error-free, and automated deactivation sequences.