Windows NT Services

Many services that run quietly and independently in the background support Windows NT. If you understand the functions of these services, you can improve your system's performance by running only necessary services. In this article, I will discuss what running software as a service means. I will look at some NT services and examine why they are important to the functioning of your computer and your network. Then I will show you how evaluating services with an eye toward eliminating the ones you don't need can fine-tune your system's performance.

Running as a Service
What does it mean when a program or component of NT runs as a service? Typically, when an application runs on an NT computer, the user starts it after logon. Some applications might start during the logon process if they are listed in the Startup folder. But a service program always starts independently of the logon: NT starts its service programs as part of the startup process, even if no one logs on to the computer. In the case of a computer that functions as a server, service programs must begin automatically during the startup process, because no one logs on to servers except to perform systems administration tasks (and sometimes an administrator will perform these tasks remotely).

Some NT applications, most notably BackOffice, run as services. SQL Server usually starts as a service when NT starts. Starting automatically with NT lets SQL Server process queries and act as a back-end application for clients without requiring a user to log on first. Systems Management Server (SMS) is another application that starts multiple services automatically.

Finding Your System's Services
To find out what services are running on your system, from the Start menu, select Settings and Control Panel and double-click Services. If you access Services right after you start NT, you might see the message "Service Database is locked." This message means that some services are still loading and initializing in the background, so you can't get to the list of services just yet. If you wait a few seconds, you'll be able to bring up the dialog box. NT offers another way to open this list: From the Start menu, select Programs, Administrative Tools, Server Manager. From Server Manager, select your computer, and select the Computer, Services menu item. If you have the appropriate privileges, this second method lets you see what services are running on a remote computer: Simply select the remote computer from Server Manager, and then select Computer, Services from the menu.

Screen 1, page 216, shows the Services dialog box with various services listed. The Status column tells you whether a particular service has started. The Startup column shows you whether a service is set to start automatically upon system startup or manually (manual services start when an application or another service calls them). The Startup column will also show when a service is disabled, in which case it will not start at all. The Startup button in the Services dialog box lets you modify these options, but NT usually automatically sets the options correctly at the time the service is installed (see Screen 2, page 216, to view the Startup options).

Starting and Stopping Services
Sometimes a systems administrator will need to stop and start services. For example, when you make a change to SQL Server, which is a service, you must stop SQL Server to make the change and then restart it after you've made the change. You can do the stopping and starting from the SQL Server Service Manager or Enterprise Manager, or from the Services dialog box.

To stop a highlighted service in the Services dialog box, click Stop. Click Start to start the service again. Some services take a few seconds to start and stop. If you try to start or stop a service from the Services dialog box, do not be concerned if you see a message that the service is already running. You just need to wait a few seconds. If you access the list of services from the Server Manager, you can start and stop services on another computer.

Startup Accounts. Most services use the System account to start up. In other words, they run in the security context of the NT operating system. But some services, such as the Replicator service and the SQL Server SQL Executive, need to log on with specific accounts. You set up these accounts with the appropriate group memberships in User Manager for Domains. But you must also assign each account the Log on as a service right. From within User Manager for Domains, select User Rights from the Policies menu. As Screen 3 shows, be sure to select the Show Advanced User Rights check box. Next, scroll down to the Log on as a service right and add the user account. When you assign this right to the account the service uses for logon, as shown in Screen 4, you are specifying that the service can start automatically in the background with this account, without requiring that a user take any action.