dido:public:ra:1.4_req:2_nonfunc:14_reliability:02_availability
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dido:public:ra:1.4_req:2_nonfunc:14_reliability:02_availability [2020/11/14 13:28] nick |
dido:public:ra:1.4_req:2_nonfunc:14_reliability:02_availability [2021/06/09 13:59] (current) char |
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| - | ====== 4.2.2.2 Availability ====== | + | ====== 4.3.2.2 Availability ====== |
| [[dido:public:ra:1.4_req:2_nonfunc:14_reliability | Return to Reliability ]] | [[dido:public:ra:1.4_req:2_nonfunc:14_reliability | Return to Reliability ]] | ||
| ===== About ===== | ===== About ===== | ||
| [[.:02_availability | return to the top]] | [[.:02_availability | return to the top]] | ||
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| - | * **<color blue><todo @nick #char:2020-10-22>Char's review done</todo></color>** | ||
| - | * **<color #FF0000><todo @DDSFmember>Please Review</todo></color>** | ||
| [[dido:public:ra:xapend:xapend.a_glossary:a:availability]] in this context is System Availability. System Availability __is the probability__ the system will function as designed for a particular duration. The duration could be a fixed time period (i.e., 24 hours a day, 7 days a week, or 364.9 days a year) or it could be over a particular mission (i.e., a flying mission, a patient stay, or a growing season). The ability of an item to be in a state to perform a required function under given conditions at a given instant of time or over a time interval, assuming the required external resources are provided. ((**Note:** Availability is part of [[dido:public:ra:xapend:xapend.a_glossary:r:ram]])) | [[dido:public:ra:xapend:xapend.a_glossary:a:availability]] in this context is System Availability. System Availability __is the probability__ the system will function as designed for a particular duration. The duration could be a fixed time period (i.e., 24 hours a day, 7 days a week, or 364.9 days a year) or it could be over a particular mission (i.e., a flying mission, a patient stay, or a growing season). The ability of an item to be in a state to perform a required function under given conditions at a given instant of time or over a time interval, assuming the required external resources are provided. ((**Note:** Availability is part of [[dido:public:ra:xapend:xapend.a_glossary:r:ram]])) | ||
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| )) | )) | ||
| - | :{{:ddsf:private:cookbook:02_body:02_projreq:nonfunctional:screen_shot_2020-07-03_at_11.19.28_am.png?400|}} | + | :{{:dido:public:ra:1.4_req:2_nonfunc:02_availability:screen_shot_2020-07-03_at_11.19.28_am.png?400|}} |
| **Mission Duration (T<sub>m</sub>)** is the time the system needs to be operational. T<sub>m</sub> can be expressed as a fixed time period (i.e., 24 hours a day, 7 days a week, or 365 days a year) or it could be over a particular mission (i.e., a flying mission, a patient stay, peak energy demand, or a growing season) | **Mission Duration (T<sub>m</sub>)** is the time the system needs to be operational. T<sub>m</sub> can be expressed as a fixed time period (i.e., 24 hours a day, 7 days a week, or 365 days a year) or it could be over a particular mission (i.e., a flying mission, a patient stay, peak energy demand, or a growing season) | ||
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| * [[dido:public:ra:xapend:xapend.a_glossary:m:mamdt]] is the average time required to perform diagnostics and replace parts | * [[dido:public:ra:xapend:xapend.a_glossary:m:mamdt]] is the average time required to perform diagnostics and replace parts | ||
| - | ===== DDS Specifics ===== | + | ===== DIDO Specifics ===== |
| [[.:02_availability | return to the top]] | [[.:02_availability | return to the top]] | ||
| - | Please refer to the **Note** in the MBTF section above. | ||
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| - | [[dido:public:ra:xapend:xapend.a_glossary:d:data_distribution_service_dds]] systems are generally architected, designed and implemented to provide redundancy and [[dido:public:ra:xapend:xapend.a_glossary:f:failover]] in the event of a failure of [[dido:public:ra:xapend:xapend.a_glossary:s:safetycritical]] and [[dido:public:ra:xapend:xapend.a_glossary:m:missioncritical | Mission Critical Systems]]. | ||
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| - | DDS allows for multiple [[dido:public:ra:xapend:xapend.a_glossary:p:publisher | Publishers]] and [[dido:public:ra:xapend:xapend.a_glossary:s:subscriber | Subscribers]] of data to the same [[dido:public:ra:xapend:xapend.a_glossary:t:topic]] at the same time. The [[dido:public:ra:xapend:xapend.a_glossary:q:quality_of_service_qos_policies]] parameters set by each publisher and each subscriber are used to connect them together. | ||
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| - | For example, if the temperature in a chemical mixing tank is critical to the overall process, having multiple temperature sensors in the mixing tank at the same time allows for redundancy for the critical [[dido:public:ra:xapend:xapend.a_glossary:s:sensor]]. If one of the two sensors fail, the DDS [[dido:public:ra:xapend:xapend.a_glossary:m:midware]] will automatically start routing the data published by the backup sensor to the subscribers. | ||
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| - | Similarly, if the monitor listening to the Topic is considered critical to the chemical mixing process, the system can use redundant monitors. The monitors watch the data on the Topic and make adjustments to the the system to correct temperature variations thereby keeping the temperature in the correct operating range. The monitor does this by publishing information on a different Topic monitored by [[dido:public:ra:xapend:xapend.a_glossary:a:actuator | Actuators]] while making the appropriate adjustments. | ||
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dido/public/ra/1.4_req/2_nonfunc/14_reliability/02_availability.1605378526.txt.gz · Last modified: 2020/11/14 13:28 by nick
