> # Online System Health Management

> The Online Health Management System (OHMS) (system health) is a hardware fault detection and recovery feature. It ensures the general health of switching, services, and supervisor modules in any switch in the Cisco MDS 9000 Family.

> The OHMS monitors system hardware in the following ways:

> - The OHMS component running on the active supervisor maintains control over all other OHMS components running on the other modules in the switch.
> - The system health application running in the standby supervisor module only monitors the standby supervisor module, if that module is available in the HA standby mode.

> The OHMS application launches a daemon process in all modules and runs multiple tests on each module to test individual module components. The tests run at preconfigured intervals, cover all major fault points, and isolate any failing component in the MDS switch. The OHMS running on the active supervisor maintains control over all other OHMS components running on all other modules in the switch.

> On detecting a fault, the system health application attempts the following recovery actions:

> - Performs additional testing to isolate the faulty component.
> - Attempts to reconfigure the component by retrieving its configuration information from persistent storage.
> - If unable to recover, sends Call Home notifications, system messages and exception logs; and shuts down and discontinues testing the failed module or component (such as an interface).
> - Sends Call Home and system messages and exception logs as soon as it detects a failure.
> - Shuts down the failing module or component (such as an interface).
> - Isolates failed ports from further testing.
> - Reports the failure to the appropriate software component.
> - Switches to the standby supervisor module, if an error is detected on the active supervisor module and a standby supervisor module exists in the Cisco MDS switch. After the switchover, the new active supervisor module restarts the active supervisor tests.
> - Reloads the switch if a standby supervisor module does not exist in the switch.
> - Provides CLI support to view, test, and obtain test run statistics or change the system health test configuration on the switch.
> - Performs tests to focus on the problem area.

> Each module is configured to run the test relevant to that module. You can change the default parameters of the test in each module as required.

> Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.