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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Johnson Wood (7815@notesmail.huawei.com.cn )
Organization:Huawei Tech.Co.,Ltd.
Date posted: Sat Jun 10 2:54:04 US/Eastern 2000
Subject: Software Reliability Prediction
Message:
A software reliability prediction method is presented in the RAC publication NEW SYSTEM RELIABILITY ASSESSMENT METHOD.I have some questions about the table 2.2-21 in page 68: 1.What are the exact meanings of Fault Activation and Fault Latency in the box I and how to determind the values? 2.How to calculate the Inherent MTBF in box III?


Reply:

Subject: Software Reliability Prediction
Reply Posted by: Norman B. Fuqua (nfuqua@alionscience.com )
Organization: RAC
Date Posted: Tue Jun 13 9:52:50 US/Eastern 2000
Message:
The document that you are referring to represented an interim approach as far as the PRISM RACRates Software model is concerned. So I will try to address your questions from the perspective of the actual PRISM RACRates Software model rather than that document. Fault Latency is a dimensionless quantity it is the average number of times that a failure is expected to reoccur before its underlying fault is corrected. Fault Activation (in %) is the % of the population exhibiting fault activation. The default values used by PRISM for these to parameters, assuming that it is not a widely deployed system, are: Fault Latency = 2, Fault Activation = 100%. The Inherent MTBF that appears in Box III is not used in the model. Due to the limitations of this media I am unable to copy the actual software model here but I will email it to you seperately.


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