Fault tolerance management

The hardware and software used to implement LIMS systems must be vahdated. Computers and networks need to be examined for potential impact of component failure on LIMS data. Security concerns regarding control of access to LIMS information must be addressed. Software, operating systems, and database management systems used in the implementation of LIMS systems must be vahdated to protect against data cormption and loss. Mechanisms for fault-tolerant operation and LIMS data backup and restoration should be documented and tested. One approach to vahdation of LIMS hardware and software is to choose vendors whose products are precertified however, the ultimate responsibihty for vahdation remains with the user. Vahdating the LIMS system s operation involves a substantial amount of work, and an adequate vahdation infrastmcture is a prerequisite for the constmction of a dependable and flexible LIMS system. 

Wensley, J. H., Improved Alarm Management through Use of Fault Tolerant Digital Systems, Instrument Society of America, International Conference and Exhibit, Houston, TX (Oct. 13-16, 1986). 

At the same time, by introducing a service management platform which separates tools, documents, etc. from physical resources, management of efficient and fault-tolerant execution of development tools can be integrated transparently [422]. The service platform includes various functionality to do so. A basic functionality is the integration of a service trader which can find... 

The rehabdity modeling of fault-tolerant aircraft systems using SyRelAn can be divided into two modeling levels, one mapping the system architecture, the other defining the redundancy management. Therefore the SyRelAn tool uses ReUabdity Block Diagrams for the definition of the nominal system architecture. To map the multi-state behavior of different components Concurrent Finite State Machines are implemented. 

This contribution has shown the recent advancements of the software tool S yRelAn and underlying methodology, which can be utilized in the pre-design of fault-tolerant systems within the context of rehability analysis and redundancy management. The hybrid system model forms the basis of this reliabihty analysis, consisting of an upper-level Reliability Block Diagram and a lower-level Concurrent Finite State Machine environment. 

Rehage, D, Carl, U. B., Vahl, A. 2005, Redundancy Management of Fault Tolerant Aircraft System Architectures -Reliability Synthesis and Analysis of Degraded System States. Aerospace Science and Technology, Volume 9, Issue 4, pp. 337-347. 

This Fault liijection Architecture is composed by the FIM (Fault liijector Manager). The FIM (Fig. 2) is designed to d3mamically anal3 e systems that need verification of reUabUity requirements. The flexible verification of the MUT enables the fault tolerance mechanism to be proved. It is also possible to verify the correct management of the defect according to the specifications. 

The HSE study demonstrates that attention to detail is essential in the design and management of SIF. Inadequate procedures, training, and MOC contribute to SIF failure as readily as random hardware failure. Improper operational or maintenance activities can completely disable an SIF, no matter how fault tolerant the SIF design. To combat these errors, operation and maintenance procedures should be clear and consistent with operator or maintenance technician expectations to reduce the potential for error. Back-checks and independent confirmation should be used to verify that the SIF is operational after any maintenance activity. Design practices can also reduce operator or maintenance technician errors that could potentially lead to failure. 

The second case considered by the standard is where the SIS is not fault tolerant and is providing protection in a demand mode. Continued operation within the MTTR is taken into account in the calculation of the probability of random hardware failure. However, in this case, there is no protection until the faulted device is repaired and returned to service. Therefore, when continuing operation with a disabled SIF, compensating measures should be identified that provide risk reduction equivalent to that provided by the SIF in the absence of the fault. These compensating measures should be documented in the operation and maintenance procedures so that personnel are trained on their appropriate use. To continue operation beyond the MTTR, a management of change review should be conducted to ensure that the compensating measures identified are sufficient for extended operation and that priority has been placed on the repair. 

The anomaly management metric (SA) degree to which fault tolerance exists in the software studied. The traceability metric (ST) degree to which the software being implemented matches the user requirements. 

Integrating a system under fault-free conditions, then assessing the fault tolerance or failure management following installation. 

White Paper, Ethernet Fault Tolerance and Redundancy, Emerson Process Management, March 2007. 

Aljer and Devienne [5] consider the use of a formal specification language as the foundation of real validation process. They propose architecture based upon stepwise refinement of a formal model to achieve controllable implementation. Partitioning, fault tolerance, and system management are seen as particular cases of refinement in order to conceptualize systems correct by proven construction. The methodology based on the refinement paradigm is described. To prove this approach, the B-HDL tool based on a combination of VHDL and B method formal language has been developed. 

In the next subsections, we present three different attacks that we carried on our experimental kernel. Two of the attacks target the core functions of the system, more precisely, the memory management and the time mangement. The third attack target the fault tolerance mechanisms. 

The first line of defence against hazardous failure conditions is avoidance, in which design and management techniques should be applied to minimise the likelihood of faults arising from random or systemic causes (see Section 6.5). The second line of defence is based on the provision of fault tolerance as a means of dynamic protection during system operation. Possible approaches include ... 

The Project shall comply with the Prometheus Single Point Failure Policy as documented in the Prometheus Project Policies Document 982-00057. (Level 2 Requirement) Structure and thermal management subsystems must be designed with fault tolerant capacity. This would include features such as ability to react flight loads in presence of element failure (with reduced margin) and redundant heaters and temperature sensors. Micrometeoroid and orbital debris protection reduce the risk in areas where single point failure can not be eliminated, such as the pressure boundaries. 

The mechanical interface of an SAS is an important aspect to be taken into account during development of the SAS. If tolerances are not properly managed by the interface specification an additional superimposed nonlinearity will be the consequence. This additional fault angle is not created by the SAS itself, it is overlaid through its interface with other parts and their inherent tolerances (e.g., bearings, rotating shaft amongst others). 

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