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Display Name (?):

COM+ Event System

Short Name (?):

EventSystem

Executable (?):

svchost.exe

Library (?):

es.dll

Depends On (?):

Remote Procedure Call (RPC)

Supports (?):

File Replication, System Event Notification, Windows Internet Name Service (WINS)

Description (?):

Supports System Event Notification Service (SENS), which provides automatic distribution of events to subscribing Component Object Model (COM) components. If the service is stopped, SENS will close and will not be able to provide logon and logoff notifications. If this service is disabled, any services that explicitly depend on it will fail to start.

OS (?):

2000 Professional, XP Home/Professional, Vista Home/Business, 2000 Server, Server 2003, Vista Server

Startup (?):

Default	Home	Workstation	Server	Minimal	Tweaked	Automatic
Manual	Automatic	Automatic	Automatic	Automatic	Disabled	Automatic

Explanation (?):

The COM+ event system is a very critical component of Windows. The main purpose of COM+ is to use message passing that allows different components to talk with each other without knowing exactly the identify of the other processes. This allows an application to broadcast the need for something and another active program or service to answer the call with the answer. Ideas behind the COM+ event system tell the Windows executive to terminate no longer used libraries, to call required shared libraries and to negotiate their use.

From a technical standpoint what the COM+ does is hide the implementation of components with a standardized data flow interface. By allowing a single standard flow control mechanism to handle all components the system can, in theory, load only what it needs when it needs it and get rid of them when it doesn't. This method also allows for inheritance of modules which further reduce load. Due to the inheritance features it also provides a security model for protecting applications with differing privileges. An example of this is the loading and unloading of DLLs through the use of DLLHOST.EXE. This mechanism loads shared dynamically linked library (DLL) files when required by an application and allows other applications that use them to share the single loaded set. When all applications that require them are terminated the DLLs themselves are removed in a garbage collection.

Needless to say this is very important to have running and should never be disabled. Doing so may end up disabling the proper use of the system as the COM+ system not only controls applications but also other services. An example of this is the logon service which depends on the COM+ system, so disabling the COM+ system would make it impossible to startup Windows. In normal circumstances it is best to leave this service as it is, but I recommend setting it to automatic.