当多个 SQL Server 实例在同一台计算机上运行时，每个实例都有自己的 SQL Server 服务。默认实例的服务名称为 MSSQLServer
sqlserverAgent SQL Server 代理服务
SQL Server 代理程序支持的功能包括：允许在 Microsoft® SQL Server™ 2000 上调度定期执行的活动，以及通知系统管理员服务器所发生的问题
sqlserverAgent SQL Server 代理服务
SQL Server 代理程序支持的功能包括：允许在 Microsoft® SQL Server™ 2000 上调度定期执行的活动，以及通知系统管理员服务器所发生的问题
The Microsoft® SQL Server™ 2000 database engine runs as a service on the Microsoft Windows NT® or Microsoft Windows® 2000 operating systems. It does not run as a service on Microsoft Windows 98 because this operating system does not support services. SQL Server can also run as an executable file on Windows NT and Windows 2000, although it is usually run as a service.When multiple instances of SQL Server are run on the same computer, each instance has its own SQL Server service. The service name for the default instance is named MSSQLServer, the service name for named instances is MSSQL$InstanceName. For more information, see Multiple Instances of SQL Server.The SQL Server service manages all of the files that comprise the databases owned by an instance of SQL Server. It is the component that processes all Transact-SQL statements sent from SQL Server client applications. SQL Server also supports distributed queries that retrieve data from multiple sources, not only SQL Server.The SQL Server service allocates computer resources effectively between multiple concurrent users. It also enforces business rules defined in stored procedures and triggers, ensures the consistency of the data, and prevents logical problems such as having two people trying to update the same data at the same time.
SQL Server Agent supports features allowing the scheduling of periodic activities on Microsoft® SQL Server™ 2000, or the notification to system administrators of problems that have occurred with the server. The SQL Server Agent components that implement this capability are: Jobs
Defined objects consisting of one or more steps to be performed. The steps are Transact-SQL statements that can be executed. Jobs can be scheduled, for example, to execute at specific times or recurring intervals.Alerts
Actions to be taken when specific events occur, such as a specific error, errors of certain severities, or a database reaching a defined limit of free space available. The alert can be defined to take such actions as sending an e-mail, paging an operator, or running a job to address the problem.Operators
People identified through their network account or e-mail identifier (ID) who can address problems with the server. They can be the targets of alerts, either through e-mail, a pager, or a net send network command.The service name of SQLServerAgent applies only to the Agent service associated with a default instance. SQL Server Agent services associated with named instances are named SQLAgent$InstanceName.
The Microsoft Distributed Transaction Coordinator (MS DTC) is a transaction manager that allows client applications to include several different sources of data in one transaction. MS DTC coordinates committing the distributed transaction across all the servers enlisted in the transaction.An installation of Microsoft® SQL Server™ can participate in a distributed transaction by: Calling stored procedures on remote servers running SQL Server.
Automatically or explicitly promoting the local transaction to a distributed transaction and enlist remote servers in the transaction.
Making distributed updates that update data on multiple OLE DB data sources.
If these OLE DB data sources support the OLE DB distributed transaction interface, SQL Server can also enlist them in the distributed transaction.The MS DTC service coordinates the proper completion of the distributed transaction to ensure that either all of the updates on all the servers are made permanent, or, in the case of errors, all erased.
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