Here’s a tip that can improve your ArcGIS Server for the Microsoft .Net Framework performance if your web services are receiving many requests over an extended period of time.
When someone makes a request from one of your web services, the web server must authenticate itself with the Server Object Manager (SOM). The web server accomplishes this by impersonating a user in the AGSUSERS group, namely the ArcGIS Web Services account that you entered when you ran the post install. This impersonation doesn’t cost much under light loads, but under heavy loads the Local Security Authority Subsystem Service (Lsass.exe) can become overworked, causing a noticeable lag in performance. Heavy loads are considered 25 or more requests per second.
You can avoid this per-request impersonation by configuring your web services to run in an application pool that runs under the identity of the ArcGIS Web Services account. This lightens the load on the Lsass.exe process and ultimately allows your services to run faster.
These ESRI Knowledge Base articles give additional background on the problem and describe how to make the adjustments to your configuration.
- ESRI Knowledge Base Article #32620 (Windows Server 2003)
- ESRI Knowledge Base Article #32622 (Windows XP)
A final note- You’re not as likely to encounter this problem with cached map services because users only need to authenticate with the SOM once, when they initially connect to the service. After that, they can retrieve cache tiles directly from the virtual cache directory.
-Sterling Quinn and Eric Miller
