W3WP and SOM processes consume too much memory when GIS services are under heavy load

Description

The IIS W3WP worker process and SOM process may begin to adversely affect other applications by consuming large amounts of memory when GIS Services are under very heavy load.

Cause

The .NET garbage collection has a concept of generations (Garbage Collector Basics and Performance Hints). Local variables and short term objects are classified as generation one and are cleaned up frequently when garbage collection is called. Objects that have longer lifetimes are classified as generation two or higher and are less frequently cleaned up when garbage collection is called.

ArcGIS Server DCOM runtime callable wrapper (RCW) proxies and their references to DCOM objects in the SOM process are particularly susceptible to being pushed into higher generations and accumulate on the Web server and SOM until the less frequent second or third generation garbage collection algorithm occurs.

Under load, when second and third generation garbage collection may be delayed due to its high CPU utilization cost, the W3WP and SOM process memory utilization can grow rapidly.

Solution or Workaround

1. Navigate to the ArcGIS Server Web service instance directory. This is typically:
   
   C:\Inetpub\wwwroot\ArcGIS\Services
2. Open the web.config file in a text editor, such as Notepad.
3. Edit the GCInterval key in the <appSettings> subElement of the <configuration> element by changing the value from the default of 10000 to something smaller.
   
   

   Code:
   <configuration>
      ...
      <appSettings>
         ...
         <add key="GCInterval" value="1000" />
         ...
   </configuration>

   
   
4. Restart IIS by issuing 'iisreset' in a command window or by restarting the IISAdmin windows service.
   
   
   1. Open the Services control panel from Start > Control Panel > Administrative Tools > Services.
   2. In the local services pane, select 'IIS Admin Service' and click the restart link or button.