SQL Server Architecture

SQL Server Architecture :

• Services,
• Instances,
• Tools.

Services:

In Windows, services are applications that start without user interaction, typically at computer startup. When SQL Server is installed, multiple services are setup on the computer. These include some or all of the following, depending on the options chosen during installation:


SQL Server 2012 database engine, which is responsible for executing commands submitted in the Transact-SQL, or T-SQL, language, database management,memory and disk allocation, and other core features of SQL Server.


SQL Server Agent, which is responsible for executing scheduled jobs, monitoring the system for defined alert conditions, and other administrative tasks.


Business intelligence components, which include SQL Server Reporting Services, SQL Server Analysis Services, and SQL Server Integration Services.

Instances:       

The basic unit of installation and program execution for SQL Server is an instance. An instance is a copy of the SQLSERVR.EXE executable program, which runs as a Windows service. Logically, an instance represents the programs and resource allocations that support a single copy of SQL Server running on a computer, such as memory, configuration files, and CPU. Multiple instances of SQL Server may be installed side-by-side on a single computer, whether the computer is a physical or a virtual server. 

Each instance is isolated from other instances on the same computer, including disk files used, security permissions, and resources allocated. The exception to this is shared components such as management tools and documentation.

One of the instances may be set up as the default instance, which means you will access it using only the name of the host computer. All other instances on the same computer must be named instances, which you will access using a combination of the host name and the instance name.

Tools :

SQL Server ships with a number of tools to manage, develop with, and query the database engine.

SQL Server Management Studio, or SSMS. SSMS is an integrated management, development, and querying application with many features for exploring and working with your databases.

SQLCMD, a command-line client that allows you to submit T-SQL commands as an alternative to using the graphical SSMS application.

SQL Server Configuration Manager, which while primarily a tool for administrators, also includes features useful for managing SQL Server software installed on client machines, such as the ability to create and manage aliases to SQL Servers.