Set the default scan intervals

Set the time when the most recent service data becomes stale if no new data has not been received. Also set the default scan interval, the time between each scan of the service.

When monitoring a device, the agent or probe scans the service after the specified scan interval and sends data to the central server. If the Time-to-Stale (TTS) value elapses before the agent or probe sends any new data, the state of the service changes to Stale. However, a high volume of network traffic can cause a delay in sending data to the central server. If the specified TTS value is too close to the scan interval value, the service can constantly be in the Stale state. To avoid this, ensure the TTS is at least twice the scan interval. The Event Log service does not require a TTS value; it receives events as they occur.

During an upgrade of the central server, if the default values of the time-to-stale and scan intervals have been changed, you need to specify their settings again after the upgrade.

This feature is only available at the system or product administrator level.

1. Go to Administration > Service Management > Default Scan Intervals.
2. In the Default Scan Interval column, enter one of the following values:

   • An integer value, in minutes.

   • A Quartz cron expression.

   Standard 5-field UNIX cron expressions are not supported.

3. For each service, select Propagate only if you would like to apply any changes to the settings to all of the devices that are running this service. Otherwise, the changes are applied only to the new devices.

   The Interval Type column indicates the type of value that can be entered for the scan interval.

4. Select Save.

About Quartz scan interval expressions

N-central agent and probe tasks use Quartz cron expressions, which require a leading seconds field and contain 6 or 7 fields. You can use the Quartz cron expression generator to create and validate expressions.

Standard 5-field Unix cron expressions, for example */30 * * * *, aren't supported. Using a 5-field expression generates an "Unexpected end of expression" error. Service scanning stops, but the service status continues to appear normal.

Quartz expression requirements

Use a Quartz expression that meets the following requirements:

• Use 6 or 7 fields. The 7-field format includes an optional year.

• Include the seconds field as the first value.

• Specify ? in either the Day of Month or Day of Week field.

• Do not use * in both the Day of Month and Day of Week fields.

If the schedule does not run as expected, review the agent log for Quartz scheduler parsing or format errors.

Common conversions