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Games - Microsoft Data Access Components


Microsoft Data Access Components (commonly abbreviated MDAC), is a group of Microsoft
technologies that interact together as a framework that allows programmers a uniform and comprehensive way of developing applications for accessing almost any data store. It is made up of various components: ActiveX Data Objects
(ADO), OLE DB
, and Open Database Connectivity (ODBC). There have been several deprecated components as well, such as the Microsoft Jet Database Engine
, MSDASQL, and Remote Data Services
(RDS). Some components have also become obsolete, such as the former Data Access Objects
API and Remote Data Objects
.

The first version of MDAC was released in August 1996, and according to statements from Microsoft was more of a concept than a stand-alone program and had no widespread distribution method, though later Microsoft released upgrades to MDAC as web-based redistributable packages. Eventually, later versions were integrated with Microsoft Windows
and in MDAC 2.8 SP1 they ceased offering MDAC as a redistributable package. Throughout its history MDAC has been the subject of several security flaws, which lead to attacks such as an escalated privileges attack, although the vulnerabilities were generally fixed in later versions and fairly promptly. The current version is 2.8 service pack 1, but the product has had many different versions and many of its components have been deprecated and replaced by newer Microsoft technologies.

Architecture

The latest version of MDAC (2.8) consists of several interacting components, all of which are Windows
specific except for ODBC (which is available on several platforms). MDAC architecture may be viewed as three layers: a programming interface layer, consisting of ADO and ADO.NET
, a database access layer developed by database vendors such as Oracle and Microsoft (OLE DB
, .NET managed providers and ODBC drivers), and the database itself. These component layers are all made available to applications through the MDAC API. The Microsoft SQL Server
Network Library, a proprietary access method specific to Microsoft SQL Server, is also included in the MDAC. Developers of Windows applications are encouraged to use ADO or ADO.NET for data access, the benefit being that users of the application program are not constrained in their choice of database architecture except that it should be supported by MDAC. Naturally, developers still have the choice of writing applications which directly access OLE DB and ODBC.

Microsoft SQL Server Network Library

The Microsoft SQL Server Network Library (also known as Net-Lib) is used by the Microsoft SQL Server to read and write data using many different network protocols. Though Net-Lib is specific to the SQL Server, Microsoft includes it with MDAC. The SQL Server uses the Open Data Services (ODS) library to communicate with Net-Lib, which interfaces directly with the Windows NT
operating system line's Win32 subsystem. The SQL Server Network Library is controlled through the use of a Client Network Utility, which is bundled with the SQL Server.

Each Net-Lib supported network protocol has a separate driver (not to be confused with a device driver), and has support for a session layer in its protocol stack. There are two general types of Net-Lib: the primary and the secondary. The primary Net-Lib consists of a Super Socket Net-Lib and the Shared Memory Net-Lib, while there are numerous secondary Net-Libs, including TCP/IP and named pipes network libraries (named pipes are a method of communicating with other processes via a system-persistent pipeline that is given an identity). The Microsoft OLE DB Provider for SQL Server (SQLOLEDB) communicates via primary Net-Libs.

[ Visit the complete Wikipedia entry for Microsoft Data Access Components ]


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