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Urgent patches could be from a critical (See Understanding Severities in the SECURITY JIRA Queue) security vulnerability that cannot be mitigated or for something that destabilizes the system or a subcomponent. After the update a full vulnerability scan is run for confirmationinstall the efficacy of the changes are tested.
When possible these are done in a rolling update to avoid complete system outages, but it can require and entire unplanned outage. In these cases customers are promptly notified of the plan, and the outage will be posted on the NCSA service status page unless further discretion is required by the customer.
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