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Database tuning describes a group of activities used to optimize and homogenize the performance of a database. It usually overlaps with query tuning, but refers to design of the database files, selection of the database management system (DBMS) application, and configuration of the database's environment ( operating system , CPU , etc.).
Every request received by a non-failing node in the system must result in a response. This is the definition of availability in CAP theorem as defined by Gilbert and Lynch. [ 1 ] Note that availability as defined in CAP theorem is different from high availability in software architecture.
Formally, a "database" refers to a set of related data accessed through the use of a "database management system" (DBMS), which is an integrated set of computer software that allows users to interact with one or more databases and provides access to all of the data contained in the database (although restrictions may exist that limit access to particular data).
For example, think of A as Authors, and B as Books. An Author can write several Books, and a Book can be written by several Authors. In a relational database management system, such relationships are usually implemented by means of an associative table (also known as join table, junction table or cross-reference table), say, AB with two one-to-many relationships A → AB and B → AB.
Also, most commercial data analysis tools are used by organizations for extracting, transforming and loading ETL for data warehouses in a manner that ensures no element is left out during the process (Turban et al., 2008). Thus the data analysis tools are used for supporting the 3 Vs in Big Data: volume, variety and velocity. Factor velocity ...
The relational model was introduced by E.F. Codd in 1970 [2] as a way to make database management systems more independent of any particular application. It is a mathematical model defined in terms of predicate logic and set theory , and implementations of it have been used by mainframe, midrange and microcomputer systems.
Both a schema and a database can be used to isolate one table, "foo", from another like-named table "foo". The following is pseudo code: SELECT * FROM database1. foo vs. SELECT * FROM database2. foo (no explicit schema between database and table) SELECT * FROM [database1.] default. foo vs. SELECT * FROM [database1.] alternate. foo (no explicit ...
While the performance metric for most database systems is throughput or transactions-per-second, the performance metric of a hard real-time database system is the ratio of committed-to-aborted transactions. This ratio indicates how effective the transaction scheduling policy is, with the ultimate goal of meeting deadlines 100% of the time.