Software failure

Software failure Eollow strict controls throughout the software resulting in haz- life cycle including requirement specifications, ardous event. software design, coding, testing, and... 

Latent Human Error/Failure (management level) A management level human error is an inadequate or nonexistent management policy which creates the preconditions for active or latent human, hardware, or software failures. 

Software is not a physical entity and, unlike some hardware failures, software failures occur without advanced warning. One of the most common software failures is branching, that is, the ability to execute alternative series of commands based on differing inputs. The software branching capacity makes the commands extremely complex and difficult to validate once errors occur as an answer of a specific input, and until the introduction of that specific input error has not been detected. Software input can be almost any data and, and since it is impossible to introduce all data into a software, validation of data is extremely difficult. Thus, results are considered to be of high confidence level. The majority of software problems occur as a consequence of errors in the software design and development and are not directly related to the software manufacture. It is simple to manufacture several software copies that work perfectly and as the original one. 

After the system has been released for operation, system maintenance activities take over. The importance of such activities is characterized by recent FDA remarks related to the lack of change control management by regulated organizations. The FDA s analysis of 3140 medical device recalls conducted between 1992 and 1998 reveals that 242 of them (7.7%) are attributable to software failures. Of those software related recalls, 192 (or 79%) were caused by software defects introduced when changes were made to the software, after its initial production and distribution. 

Database Integrity. Integrity of the database must be assured particularly if the data are to be used to meet government regulations or used as legal evidence. Several things can be done to secure the data against user errors and hardware or software failures. 

A worksheet (data base spreadsheet) form is used to collect and collate the process hazard analysis review data. A computer software generated spreadsheet is typically used. For a complete description of commercially available HAZOP or What-If software, the user should refer to the manufacturer s HAZOP or What- If software User Instructions. Although pre-printed forms may be used, they are highly inefficient and should be maintained only as a backup in case of computer hardware or software failures. 

Procedures and plans supporting business continuity (Disaster Recovery Plans and Contingency Plans) must be specified, tested, and approved before the system is approved for use. Business Continuity Plans will normally be prepared for a business or an operational area rather than for individual computer systems. It is likely that the only way to verify the plan is to walk through a variety of disaster scenarios. Topics for consideration should include catastrophic hardware and software failures, fire/flood/lightning strikes, and security breaches. Alternative means of operation must be available in case of failure if critical data is required at short notice (e.g., in case of drug product recalls). Reference to verification of the Business Continuity Plans is appropriate during OQ/PQ. 

Procedures and plans supporting business continuity must be specified, tested, and approved before the system is approved for use. Topics for consideration should include catastrophic hardware and software failures, fire/flood/lightning strikes, and security breaches. Procedures need to address ... 

System timing, in particular any handshaking that may be done with other systems Software failure and restart routine Critical fault trees... 

Suppliers should have established standards to govern the development of software. The objective of such standards is to ensure a consistent and structured approach to the development of software, thus minimizing the risk of software failure and enhancing software maintainability, avoiding personal style while trying not to suppress creativity. 

Suppliers should conduct SCRs on all critical software modules in order to capture deviations from programming standards, identify logic errors, and ensure software modularity. Tailored software developed to satisfy user requirements not catered for within the standard product offering should be a particular focus of attention as the risk of software failure increases for new software developments. SCRs should be documented in order to record observations raised against the software and resultant corrective actions. Further, documented evidence of the implementation of corrective actions should be available for inspection. Where software modules present a major risk to GxP compliance or evidence of internal SCRs is limited, the pharmaceutical organization should consider additional independent reviews. Table 31.12 details the scope and content of programming standards. 

The risk of software failure requires that procedures be established and documented to minimize and manage their occurrence. Where appropriate, redundant systems must be installed, and periodic system backups must be... 

When Common Cause Failure is not a concern due to the use of diversity, the software failure modes can be considered at processing unit level only. 

Principles of software faults and software failure modes... 

A software component designed and coded either manually or with the help of tools may be subject to a wide variety of faults. The root cause of these faults is to be found in the specification, in the design or in the implementation. A software fault can be seen as a deviation in the content and/or in the order of instructions or data stored in memory causing the microprocessor not to behave as expected under some event or sequences of events. Trying to consider all possible faults that could affect even a simple software component is not practicable. Nevertheless, it is possible to consider the consequences of such faults, as they will lead to a few numbers of software failure modes... 

Definitions of software failure modes in the context of SPINLINE3 software... 

In this paper, we have presented this software FMEA experienee including adaptation of the principles of FMEA to analyze a software program choice of a block of instmction (BI) approach to identify the components to analyze definition of the software failure modes associated with the Bis examples of the analyses performed on the SPINLINE3 Operational System Software feedback of experience... 

Software failure A dynamic problem with a piece of software. 

Braasch, A., Specht, M., Meyna, A., Hubner, H.-J. 2007. An approach to analyze software failure behavior of automotive telecommunication systems. Proceedings of ESREL 2007. London Taylor Francis Group. 

Figure 2. Composition of types of software failures in displaying.

Xie, M. and C. Wohlin (1995). An additive reliability model for the analysis of modular software failure data. Proceedings of the 6 th International Symposium on Software Reliability Engineering (ISSUE 95), 188-194. 

The required SIL designates the methods and measures that have to be executed during the overall safety lifecycle phases. The SIL is a probabilistic quantitative concept. If certain techniques and measures are applied one expects on average that a certain reliability of the safety functions is realized. Besides statistic and systematic hardware errors this concept also takes systematic software failures into account. 

On the other hand, this way of software failure modelling is able to show the difference between systems with and without software diversity. 

From the text above one could conclude that separate modelling of software failures as basic events within FTA does not make a big sense, when all mentioned assiunptions are committed - i.e. simple straightforward algorithm prepared and verified based on the up-to-date standards with well done life cycle management. The only point why this is not true is a suspicion from Common Cause potential. 

Kristiansen, M. (2005). Finding upper bounds for software failure probabilities - experiments and results. Proceedings of the 24th International Conference on Computer Safety, Reliability and Security (Safe-comp 05), 179-193. 

A challenge is to find ways to link registration of software failures into the maintenance systems. 

We assume therefore that signals - only associated to local errors - are the only elements leading to the feared event. The other propagation phenomena, as those due to atmospheric delays, are then supposed corrected inside the receiver. Neither material or software failure is supposed to occur in ground or satellite facilities this means that signals are broadcasted by the satellites without interruption and without fault in the transmitted data. 

Functional safety, as we know it today, stemmed from the computer. The versatility of computers in performing control tasks soon caused designers to consider using them for performing safety tasks, although with some trepidation since computer failure modes, especially software failures, were of concern. 

Safety of software is equal in importance to that of the hardware elements, as consequences of a software failure in medical devices can be quite serious. For example, a program that is out of control because of a software error can drive a radiation therapy machine gantry into a patient [9]. A Food and Drug Administration (FDA) study conducted over six years (1983-1989) reported that there were 116 problems in software quality that resulted in the recall of medical devices in the United States [3]. Most of the methods and techniques that can be used to improve software safety in medical devices are available in Refs. [10-12]. 

The review of data and evaluation of the run for acceptance based on the criteria established during method validation can be found in Section 10.5.3, but in this section the instance considered is that when the analytical run fails prior to completion of the inj ection sequence or upon inspection of the data and it is apparent that there was a hardware or software failure of some kind. For events of this kind the system will need to be checked for performance to determine the nature of the failure, and repaired if necessary prior to resumption of any additional analyses. Examples for reasons why a run could fail prior to completion include hardware or computer failure, intermittent software failures, clogged injectors or broken syringes. 

Creep can be defined as deformation that occurs over time when the material is subjected to constant stress at constant temperature. In this investigation, the creep was measured in tension. The molded tensile bars with 0.5-in. taper were placed in an Instron 1331 servohydraulic testing machine, in load control, using a fixed mean level of 120 kg, and an amplitude of zero. The elevated test temperature of 80°C is achieved using a Thermotron environmental chamber. Testing is controlled by an IBM-compatible PC running Instron MAX software. Failure times (hours to creep rupture) were averaged for three specimens. 

For critical areas, where the HEA reveals that the HITs are unrealistic, mitigations can be re-assessed and recommendations developed for further action. In this way, no predictions are being made about the human error rates rather, the HITs are derived from the remaining integrity requirements once the hardware and software failure data is input and an analysis is undertaken to ascertain if the remaining human integrity requirements are realistic. 

However, all the above research studies have focused on secret key distribution issues, while the specific and unique challenge in biometric authentication, ie, how to merge the payload with the biometric information while preserving the statistical uniqueness of the biometric information, has not been addressed. Furthermore, all the above-mentioned biometric-based key-exchange schemes need critical time synchronization because they need to record biometric information simultaneously at different positions of the same human body, which incurs considerable extra communication overhead in extremely resource-constrained wearable body sensor networks. In addition, one of the biometric features may not be unique and accidental faulted measures (eg, due to hardware or software failures) may malfunction the traditional biometric-based security system. 

Combination with hard- and software failure probabilities... 

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