Database connection: Difference between revisions

Revision as of 23:28, 5 December 2018

Revision as of 19:02, 7 December 2018

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Connections are built by supplying an underlying [[software driver|driver]] or [[provider]] with a [[connection string]], which is a way of addressing a specific [[database]] or [[server (computing)|server]] and instance as well as user authentication credentials (for example, '''''Server='''sql_box;'''Database='''Common;'''User ID='''uid;'''Pwd='''password;''). Once a connection has been built it can be opened and closed at will, and properties (such as the command time-out length, or [[transaction]], if one exists) can be set. The Connection String is composed of a set of key/value pairs as dictated by the data access interface and data provider being used.

Many databases (such as [[PostgreSQL]]) only allow one operation to be performed at a time on each connection. If a request for data (a [[SQL]] [[Select (SQL)|Select]] statement) is sent to the database and a result set is returned, the connection is open but not available for other operations until the client finishes consuming the result set. Other databases, like [[Microsoft_SQL_ServerMicrosoft SQL Server|SQL Server 2005]] (and later), do not impose this limitation. However, databases that provide multiple operations per connection usually incur far more overhead than those that permit only a single operation task at a time.

== Pooling ==

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An application failure occurs when the connection pool overflows. This can occur if all of the connection in the pool are in use when an application requests a connection. For example, the application may use a connection for too long when too many clients attempt to access the web site or one or more operations are blocked or simply inefficient.

== References ==

* [http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdataidbconnectionclasstopic.asp IDbConnection Interface on MSDN]

* [http://betav.com/blog/billva/2007/05/managing_and_monitoring_net_co.html Managing and Monitoring .NET Connections whitepaper.]

* [http://betav.com/blog/billva/2006/06/getting_and_staying_connected_1.html Getting and Staying Connected whitepaper.]

* Hitchhiker's Guide to Visual Studio and SQL Server (7th Edition) Addison Wesley, William Vaughn, ISBN-13: 978-0321243621

== See also ==

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* [[RDBMS]]

== References ==

[[Category:Databases]]

* [http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemdataidbconnectionclasstopic.asp IDbConnection Interface on MSDN]

* [http://betav.com/blog/billva/2007/05/managing_and_monitoring_net_co.html Managing and Monitoring .NET Connections whitepaper.]

* [http://betav.com/blog/billva/2006/06/getting_and_staying_connected_1.html Getting and Staying Connected whitepaper.]

* Hitchhiker's Guide to Visual Studio and SQL Server (7th Edition) Addison Wesley, William Vaughn, {{ISBN-13: |978-0321243621 }}

==External links==

* [http://ConnectionStrings.com ConnectionStrings.com]

[[Category:Databases]]

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