Types
Industry standards for the term "Outage Duration" or "Maintenance Duration" can have different point of initiation and completion thus the following clarification should be used to avoid conflicts in contract execution: # "Turnkey" this is the most engrossing of all outage types. Outage or Maintenance starts with operator of the plant or equipment pressing the shutdown or stop button to initiate a halt in operation. Unless otherwise noted, Outage or Maintenance is considered completed when the plant or equipment is back in normal operation ready to begin manufacturing or ready be synchronized with system or grid or ready to perform duties as pump or compressor. # "Breaker to Breaker" This Outage or Maintenance starts with operator of the plant or equipment removing the power circuit (Main power breaker at "off" or "disengaged" or "On-Cooldown"), not the control circuit from operation. This still would allow for the equipment to be cooled down or brought to ambient such that outage/maintenance work can be prepared or initiated. Depending on equipment types, "Breaker to Breaker" outage can be advantageous if contracting out controls related maintenance as this type of maintenance work can be performed while main equipment is still on cool-down or on stand-by. Unless otherwise noted, this type of outage is considered complete when power circuit is re-energized via engaging of the power breaker. # "Completion of Lock-out/Tag-out" This Outage or Maintenance (sometimes mistaken for "Off-Cooldown" but not the same) starts with operator of the plant or equipment removing the power circuit, disengaging the control circuit and performing other neutralization of potential power and hazard sources (typically called Lock-Out, Tag-Out "LOTO") This point of maintenance period is typically the last phase of the outage initiation stage before actual work starts on the facility, plant or equipment. Safety briefing should always follow the LOTO activity, before any work is conducted. Unless otherwise noted, this type of outage is considered complete when the equipment has reached mechanical completion and ready to be placed on slow-roll for many heavy rotating equipment, Bump-test or rotation check for motors, etc., but must follow return or work permit per LOTO procedures. Any on-line testing, performance testing and tuning required should not count towards the outage duration as these activities are typically conducted after the completion of outage or maintenance event and are out of control of most maintenance contractors.Characteristics
Unplanned downtime may be the result of an equipment malfunction, etc.Telecommunication outage classifications
Downtime can be caused by failure in hardware (physical equipment), (logic controlling equipment), interconnecting equipment (such as cables, facilities, routers,...), transmission (wireless, microwave, satellite), and/or capacity (system limits). The failures can occur because of damage, failure, design, procedural (improper use by humans), engineering (how to use and deployment), overload (traffic or system resources stressed beyond designed limits), environment (support systems like power and HVAC), (outages designed into the system for a purpose such as software upgrades and equipment growth), other (none of the above but known), or unknown. The failures can be the responsibility of customer/service provider, vendor/supplier, utility, government, contractor, end customer, public individual, act of nature, other (none of the above but known), or unknown.Impact
Outages caused by system failures can have a serious impact on the users of computer/network systems, in particular those industries that rely on a nearly 24-hour service: * Medical informatics * Nuclear power and otherFamous outages
On Mother's Day, Sunday, May 8, 1988, a fire broke out in the main switching room of the Hinsdale Central Office of the Illinois Bell telephone company. One of the largest switching systems in the state, the facility processed more than 3.5 million calls each day while serving 38,000 customers, including numerous businesses, hospitals, and Chicago's O'Hare and Midway Airports. Virtually the entire AT&T network ofService levels
In service level agreements, it is common to mention a percentage value (per month or per year) that is calculated by dividing the sum of all downtimes timespans by the total time of a reference time span (e.g. a month). 0% downtime means that the server was available all the time. For Internet servers downtimes above 1% per year or worse can be regarded as unacceptable as this means a downtime of more than 3 days per year. For e-commerce and other industrial use any value above 0.1% is usually considered unacceptable.Response and reduction of impact
It is the duty of the network designer to make sure that a network outage does not happen. When it does happen, a well-designed system will further reduce the effects of an outage by having localized outages which can be detected and fixed as soon as possible. A process needs to be in place to detect a malfunction - network monitoring - and to restore the network to a working condition - this generally involves a help desk team that can troubleshoot a problem, one composed of trained engineers; a separate help desk team is usually necessary in order to field user input, which can be particularly demanding during a downtime. A network management system can be used to detect faulty or degrading components prior to customer complaints, with proactive fault rectification. Risk management techniques can be used to determine the impact of network outages on an organisation and what actions may be required to minimise risk. Risk may be minimised by using reliable components, by performing maintenance, such as upgrades, by using redundant systems or by having a contingency plan orPlanning
A planned outage is the result of a planned activity by the system owner and/or by a service provider. These outages, often scheduled during the maintenance window, can be used to perform tasks including the following: * Deferred maintenance, e.g., a deferred hardware repair or a deferred restart to clean up a garbled memory * Diagnostics to isolate a detected fault * Hardware fault repair * Fixing an error or omission in a configuration database or omission in a recent configuration database change * Fixing an error in application database or an error in a recent application database change * Software patching/software updates to fix a software fault. Outages can also be planned as a result of a predictable natural event, such as Sun outage. Maintenance downtimes have to be carefully scheduled in industries that rely on computer systems. In many cases, system-wide downtimes can be averted using what is called a "rolling upgrade" - the process of incrementally taking down parts of the system for upgrade, without affecting the overall functionality.Avoidance
For most websites, website monitoring is available. Website monitoring (synthetic or passive) is a service that "monitors" downtime and users on the site.Other usage
Downtime can also refer to time when human capital or other assets go down. For instance, if employees are in meetings or unable to perform their work due to another constraint, they are down. This can be equally expensive, and can be the result of another asset (i.e. computer/systems) being down. This is also commonly known as " dead time". Downtime is also generalized in a personal sense, being used to refer to a period of sleep orMeasuring downtime
There are many external services which can be used to monitor the uptime and downtime as well as availability of a service or a host.See also
* High availability * Uptime * Mean down time * Planned downtime * Carrier gradeReferences
{{reflist Engineering failures Maintenance System administration it:Tempo di fermo