Non-functional Requirement - Environmental Resiliency

Category: Resiliency

Context: Environment

Goals: When a component fails that affects the power or cooling required by a system, the repair or replacement of the failed component must be treatable as routine system maintenance rather than as a service affecting outage or emergency.

Rationale: If the availability of the system is sufficiently critical, the MTTR should not be dependent on the response time of vendors, the availability of repair parts or the availability of staff. The availability of the system therefore must be decoupled from the availability of any single environmental component.

Requirement: Failure of a single environmental component shall not cause user detectable loss of business functionality for an elapsed time more than Metric. After an elapsed time no longer than Metric, the user will be able to continue business functionality.


Level A:

A1. The user detectable loss of business functionality will be no more than 60 seconds
A2. The system will continue to meet all functional requirements
A3. The system will continue to meet all non-functional requirements other than environmental resiliency requirements.
A4. There will be no data loss

Level B:

B1. The user detectable loss of business functionality will be an elapsed time of no more than one business day.
B2. No more than the most recent one business day of transactions will be lost.

Level C:

This Level Intentionally Left Blank

Level D:

D1. The user detectable loss of business functionality will be an elapsed time of no more than five business days.

Scale: Seconds duration, business day, elapsed time

Stakeholders: ​System Managers, Operations, Facilities and Maintenance personnel

Implications: If this requirement is not met, the organization will incur decreased availability of systems and increased frequency and duration of facility and environmental related maintenance outages.

Applicability: See Enterprise Requirements Framework

Tags: Environmental, Resiliency

Status: Approved, Requirement

Author: <Author>

Revision: <Revision>


This NFR specifies that the facilities-related components that support the system have the appropriate level of recoverability and resiliency. 

Designers should engineer for routine power and cooling failures and have appropriate back up power, alternate cooling, as necessary. Facilities failure domains such as power supplies, power distribution units, air conditioning units, etc. should be considered. 

For more information, see NFR Summary