what is data consistency in a database
Full Answer. Data consistency is crucial to the functioning of programs, applications, systems and databases. Locks are measures that are used to prevent data from being altered by two applications at the same time, and ensure the correct order of processing.
In the viewpoint of database users, data should be consistent when two users access to the same data at the same time and can see the same value. In order to guarantee consistency, transaction management like 2PC (two-phase commit protocol) is necessary.
Consistency rules are vitally important while creating databases, as they are the embodiment of the business rules for which the database is being created.
6 Answers. Data integrity is more about the quality of data and goes well beyond data base management systems. DBMSs provide data consistency tools that can help with data integrity; they are one piece of the larger problem. Integrity constraints and triggers help ensure that a DBMS does not degrade (or, if you’re a pessimist,
They are not only different, they are orthogonal. Inconsistency :
A DB that reported employee Joe Shmoe’s department as Sales but that didn’t list Joe Shmoe among the employees in the Sales department would be inconsistent. It’s a logical property of the DB, independent of the actual data .
A DB that reported jOe SaleS to be a member of the Shmoe department would lack integrity. jOe SaleS isn’t a valid employee name and Shmoe isn’t a valid department. That’s not logically invalid, but it is invalid relative to the rules that govern data content .Best answer · 23Very roughly, my 2c: Integrity = strong types, no illegal values as determined by the data model & constraints, foriegn keys, unique constraints and stuff like that. Consistency = being able to read only committed data a given point in time, not the intermediate steps.8Data can be entirely consistent and entirely wrong. Data integrity is more about the quality of data and goes well beyond data base management systems. DBMSs provide data consistency tools that can help with data integrity; they are one piece of the larger problem. Integrity constraints and triggers help ensure that a DBMS does not degrade (or, if you’re a pessimist, further degrade) the integrity of the data that arrives. The way to parse the Oracle verbiage is that integrity constraints and triggers are a way to implement a subset of the business rules that define data integrity.6Probably these links may help you to get started: http://en.wikipedia.org/wiki/Data_consistency http://en.wikipedia.org/wiki/ACID#Consistency http://en.wikipedia.org/wiki/Data_integrity2From here Data consistency Execution of transaction in isolation preserves the consistency of the data. The data value stored in the database must satisfy certain consistency constraints. For example the balance on an account should not fall below $100. The DDL commands provide the facilities to specify such constraints. The database systems check these constraints every- time the database is updated. In general it can be an arbitrary predicate pertaining to the database. To check the consistency of database most of programmer depends on the constraints and these are usually costly to test. Data integrity The integrity of data refers to as “whole data at one place”. The data is in the form of tables and each table has some attributes. These are the cases where we wish to ensure that a value that appears in one relation for given set of attributes should also appear for a certain set of attributes in another relation (referential integrity). Database modification can cause violation of integrity. When the integrity constraint is violated, the normal procedure rejects the action that has actually caused the violation. You can read first chapter for ACID.1Consistency: You don’t have dates, number and letters in same column but only one of them.
This is forsed by defining column type, eg. column id number (5) means there won’t be dates nor letters in it and numbers greater then 99999 Integrity: If you have emplooyes table and departments table and department_id column in both of them (with meaning of department_id in witch employee is working) there won’t be any employee working in department that doesen’t exists in departments table.
This is forsed by referencal integrity constraint.1
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Application consistency. An application may be made up of many different types of data, various types of files and data feeds from other applications. Application consistency is the state in which all related files and databases are synchronized representing the true status of the application.
Additionally, data consistency can also refer to data that is constant over time or some other relationship. For example, if you have a weather dataset, it would be considered consistent if there were no missing days/hours (depending on your metric). In summary, data consistency is typically people in data science try
Example of Consistency Rules at Work. When a person is filling out a form online and forgets to fill in one of the required spaces, a NULL value goes to the database, causing the form to be rejected until the blank space has something in it. Consistency is the second stage of the ACID model (Atomicity, Consistency, Isolation, Durability),
If a data damage is found in the database consistency check, information about the affected tables is written to the basic log. Running database consistency check manually. The consistency check can be run interactively from the Control Panel by selecting the Tools / Database consistency tool .
Oracle Database maintains data consistency by using a multiversion consistency model and various types of locks and transactions. In this way, the database can present a view of data to multiple concurrent users, with each view consistent to a point in time.
Instead of data consistency within the scope of a single transaction, data must be consistent within the confines of many different transaction streams from one or more applications. An application may be made up of many different types of data, such as multiple database components, various types of files, and data feeds from other applications.