Hardware failures

A DBMS performs what is called transaction management. This process allows multiple users to access and store data in the database without cormption. The abiUty to do this is particularly important when data are being written to the DBMS, because power intermptions or hardware failure can cause database transactions to be incompletely processed. Transaction managers use the "all or nothing" principle all the data is written to the DBMS, ie, the transaction is completed, or none of it is written. 

Human factors, discussed in Section 4.2, enter a fault tree in the same manner as a component failure. The failure of manual actions, that prevent or mitigate an accident, are treated the same as hardware failures. The human error failure probability is conditioned by performance sluiping factors imposed by stress, training and the environment. 

Another danger of an inadequate appreciation of human causes of hazards is that the HAZOP analyst may consider a particular high risk event (identified by a guide word and deviation) to be noncredible, because he or she only takes into accoimt the hardware failures (with an extremely low probability) that could give rise to the event. When human causes are taken into accoimt, the likelihood of the event may actually be quite high. 

The decomposition approach is used, it is necessary to represent the way in which the various task elements and other possible failures are combined to give the failure probability of the task as a whole. Generally, the most common form of representation is the event tree (see Section 5.7). This is the basis for THERP, which will be described in the next section. Fault trees are only used when discrete human error probabilities are combined with hardware failure probabiliHes in applications such as CPQRA (see Figure 5.2). 

Opening segments of the IP2 PRA data analysis section describe the definitions of terms and concepts employed, the assumptions made, and limitations recognized during the data base construction. A set of 39 plant-specific component failure mode summaries established the basis for component service hour determinations, the number of failures, and the test data source for each failure mode given for each component. Generic data from WASH-1400, IEEE Std 500, and the LER data summaries on valves, pumps, and diesels were combined with plant-specific failure data to produce "updated" failure information. All the IP2 specialized component hardware failure data, both generic and updated, are contained in Table 1.5.1-4 (IP3 1.6.1-4). This table contains (by system, component, and failure mode) plant-specific data on the number of failures and service hours or demands. For some components, it was determined that specifications of the system was warranted because of its impact on the data values. 

Events in a fault tree are not restricted to hardware failures. They can also include software, human, and environmental factors. 

Process hardware, failure rate data for, 23 168t... 

Category IV - Outward rebound force and resulting hardware failure is acceptable. 

Use intrinsically-safe and redundant safety control designs when using hydrogen. Intrinsically-safe and redundant control systems help to minimize operator mistakes, such as venting, door opening, air releasing, and backup safeties in the event of a hardware failure. 

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. 

The full range of process maloperations, including system failures that might lead to process runaway will first have to be considered by a systematic evaluation of the plant and process concerned141. These may, for examplel be due to human error, hardware failure, or due to failure of a computerised sequence controller. To assess the likely/ credible maloperations accurately, it is recommended that personnel who will be operating the plant are involved in the hazard assessment. 

TIT - deals with software (flaws, malicious codes, etc.) and hardware (failures, power disruption, tampering, line tapping, electromagnetic emanation, etc.) aspects,... 

Hardware Failure Modes Signal Isolation IPC Location... 

Hard memory errors are related to a hardware failure and are reproducible. When a hard memory error occurs, the computer might issue either a Parity Error or a 201 BIOS Error or issue a series of beeps (upon startup). For example, if you are using AMI BIOS, and the computer issues one long and three short beeps on startup (other BIOSs will use different beep codes), you have a hardware-related memory error. A table of BIOS error codes is included in Chapter 10, Hardware Troubleshooting. ... 

The Restore wizard helps you restore your previous backed-up data in the event of a hardware failure, accidental erasure, or other data loss or damage. 

If a printer is not printing at all, then you should start with the DOS troubleshooting method. First, reboot the computer in Safe Mode DOS Prompt. (See the section Windows-Based Utilities for more information on Safe Mode.) Then copy a file or a directory listing to the printer port. If the file or directory listing doesn t print, the cause is most likely a hardware failure or loose cable. If it does print, then you can assume the printing problems are associated with the Windows printer drivers. 

The role of the agents is restricted to error handling and does not involve error detection. In contrast to the attempt to realize alarm correlation only with mobile agents, this implementation shows much better scalability. Unfortunately, an automated reaction to identified problems often is not that easy to realize, as it usually needs a system administrator to react (e.g. in case of hardware failure). Thus, for some faults, the correlation service only sends a notification to the administrators. 

Normally, we tune the two controllers in such a way that the roots of all eqs. (24.12) and (24.13) have negative real parts. Such tuning guarantees stability when both loops are closed [roots of eq. (24.13)], or only one is closed while the other is open [roots of eqs. (24.12)], due to a hardware failure. 

The recorded operating parameters captured by state-of-health data have great utility when a problem exists, the operator can review the most recently collected state-of-health data to diagnose the problem and determine corrective action. In addition, state-of-health data can be scanned automatically to attempt failure prediction. Reanalysis of state-of-health data from the systems described in this chapter has identified subtle hardware failures not detected by system operators until months later. 

INCIDENT CAUSES. Incident causes or initiating events should be readily identifiable in any PrHA method. Reviewers should use their experience to assure that all initiating events, including hardware failure modes, operator errors, administrative errors, and loss of utilities, are considered. If the process is in a location subject to external events, the PrHA should include relevant events such as earthquakes, traffic, weather, or accidents at an adjacent process. 

Software versus hardware failure - Hardware relates to aU physical aspects of the system and its components. This includes the application and database servers, storage systems, network connections and power supplies as well as the local peripheral equipment such as printers, monitors, keyboards, mice, etc. All... 

In complete service failure, the entire system is typically unavailable, a situation which is often called an outage. This type of unavailability may of course be either planned or unplanned and may be expected or unexpected by the individual user. Service failures are often due to catastrophic hardware failure where insufficient redundancy has been employed. The clinical risk is determined by a number of factors ... 

Design for redundant paths One helpful design feature is to provide multiple physical devices and logical paths to ensure that a single hardware failure or software error cannot prevent the operator from taking action to maintain a safe system state and avoid hazards. There should also be multiple ways to change... 

Output controls from the system are set in a safe status in case of internal hardware failure detection, loss of power supply, or detection of 1C scanning dismption,... 

---