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The ACID model is one of the oldest and most important concepts of database theory. It sets forward four goals that every database management system must strive to achieve: atomicity, consistency, isolation and durability. No database that fails to meet any of these four goals can be considered reliable.
Let's take a moment to examine each one of these characteristics in detail: * Atomicity states that database modifications must follow an "all or nothing" rule. Each transaction is said to be "atomic." If one part of the transaction fails, the entire transaction fails. It is critical that the database management system maintain the atomic nature of transactions in spite of any DBMS, operating system or hardware failure. * Consistencystates that only valid data will be written to the database. If, for some reason, a transaction is executed that violates the database's consistency rules, the entire transaction will be rolled back and the database will be restored to a state consistent with those rules. On the other hand, if a transaction successfully executes, it will take the database from one state that is consistent with the rules to another state that is also consistent with the rules. * Isolation requires that multiple transactions occurring at the same time not impact each other's execution. For example, if Joe issues a transaction against a database at the same time that Mary issues a different transaction, both transactions should operate on the database in an isolated manner. The database should either perform Joe's entire transaction before executing Mary's or vice-versa. This prevents Joe's transaction from reading intermediate data produced as a side effect of part of Mary's transaction that will not eventually be committed to the database. Note that the isolation property does not ensure which transaction will execute first, merely that they will not interfere with each other. * Durability ensures that any transaction committed to the database will not be lost. Durability is ensured through the use of database backups and transaction logs that facilitate the restoration of committed transactions in spite of any subsequent software or hardware failures. Take a few minutes to review these characteristics and commit them to memory. If you spend any significant portion of your career working with databases, you'll see them again and again. They provide the basic building blocks of any database transaction model.
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What is the ideal acid test ratio?
some where between 1 to 1.5
The acid test ratio does not include?
acid test / quick ration = quick assets / quick liablities quick assets = current assets - stock- prepaid expenses quick liablities = current liablities - bank overdraft
What does the acid test ratio not include cash or accounts receivable or supplies or inventory?
inventory
What are the potential cost of implementing a database system?
5. What are the potential costs of implementing database?When implementing a system, the cost is a very area that should be considered as well after determining it requirement, alpha and beta test are passed upon implementation it cost should had been considered. In this case of database it implementation cost includes hardware, software , maintenance and location are the regular database implementation dimension.Ø Hardware: We need something for it to live on. This could either be bought, or hired.Ø Maintenance: The system will at some point require updating - costs of this will need to be considered. There will also be essential maintenance from time to time although this may be covered under your contract if you get an external company to do it for you .If you own the hardware then you will also have to consider staffing to do the maintenance part - does your team have the skills or do you need another.Ø Software: Lots of free software lots of expensive software - what are we going to use and what the best for the job are for it.Ø Location: In the location, where and which part the earth should our system be operates from is very import, though in the case of database technologies most are hosted online in the means one can operate from anywhere or part of the earth. But is very important to consider the location of system source.By Enebeli Edwin NdudiUnisel-Malaysia
Advantage of RDBMS?
Advantages of RDMBS1. Data Structure:The table format is simple and easy for database users to understand and use. RDBMSs provide data access using a natural structure and organization of the data. Database queries can search any column for matching entries.2. Multi-User Access:RDBMSs allow multiple database users to access a database simultaneously. Built-in locking and transactions management functionality allow users to access data as it is being changed, prevents collisions between two users updating the data, and keeps users from accessing partially updated records.3. Privileges:Authorization and privilege control features in an RDBMS allow the database administrator to restrict access to authorized users, and grant privileges to individual users based on the types of database tasks they need to perform. Authorization can be defined based on the remote client IP address in combination with user authorization, restricting access to specific external computer systems.4. Network Access:RDBMSs provide access to the database through a server daemon, a specialized software program that listens for requests on a network, and allows database clients to connect to and use the database. Users do not need to be able to log in to the physical computer system to use the database, providing convenience for the users and a layer of security for the database. Network access allows developers to build desktop tools and Web applications to interact with databases.5. Speed:The relational database model is not the fastest data structure. RDBMS advantages, such as simplicity, make the slower speed a fair trade-off. Optimizations built into an RDBMS, and the design of the databases, enhance performance, allowing RDBMSs to perform more than fast enough for most applications and data sets. Improvements in technology, increasing processor speeds and decreasing memory and storage costs allow systems administrators to build incredibly fast systems that can overcome any database performance shortcomings.6. Maintenance:RDBMSs feature maintenance utilities that provide database administrators with tools to easily maintain, test, repair and back up the databases housed in the system. Many of the functions can be automated using built-in automation in the RDBMS, or automation tools available on the operating system.7. Language:RDBMSs support a generic language called "Structured Query Language" (SQL). The SQL syntax is simple, and the language uses standard English language keywords and phrasing, making it fairly intuitive and easy to learn. Many RDBMSs add non-SQL, database-specific keywords, functions and features to the SQL language.
What is a system integrator?
System integration test is aimed at testing how compatible a system is with an application. This will analyze the system requirements in the computer before installation.
Why is it important to test a database?
Many applications today rely on a backend database in order to function. If the database is not working properly, then the entire application is typically inaccessible because so much information including logins are stored in the database. Databases should be tested for boundary conditions, stress, function, and structure to ensure that everything is working as designed.
How do you know if your freon is contaminated in your hvac split system?
Do a compressor oil acid test.
In idioms What does acid test mean?
Acid test or litmus test means to try it an see. The acid test of a cake is eating it. The acid test of a new idea is seeing if it works.
Which test type do you use to check the application for problems in relation to its interaction with the hardware and system software?
Compatibility
What is an acid test?
An acid test is a rigorous test of the quality or value of something.
What acid do you use for the acid test?
For the acid test to determine the authenticity of gold, you typically use nitric acid. Nitric acid is used to test the purity of gold based on the reaction it produces with the metal.
What test is useful in diagnosis of gout?
It is a test for uric acid. High Uric acid in he blood can lead to the formation of uric acid crystals which are responsible for the pain.
What acid do you use for acide test?
what acid do you use to test gold
What are the four parts of the application for naturalization?
how many parts make up the application for naturalization?
How do you carry out database testing in any application?
No matter what the database or application, these are some basics (I have been a database administrator for over 10 years). 1. A test environment is necessary. You do not want to test or implement changes in a production environment. But, the test environment must be close enough to the production environment for the tests to actually let you know if the change/update will work or not harm production. 2. Benchmarks. If you are going to test a new job, benchmark each change and document each change. Change 1 thing at a time. Then you will know which change made it break or made it work. 3. Coolaboration. A DBA and application team must work together. Who made what change? When? Testing needs to be scheduled to make sure one group isn't making changes that will adversely affect what you are testing. There is more--lots more. but this will help you get started.
What is the difference between loadrunner and winrunner?
Loadrunner is an application (tool) which is used to put an excessive load by simultaneous logins and form submitting into the web application or web portal. Winrunnuer is used to test the functionality of the system under test M Alam
