503.2 IIS Error

Full Error message: HTTP Error 503.2 - Service Unavailable. The serverRuntime@appConcurrentRequestLimit setting is being exceeded.


  • When you try to go to the Recast Management Server interface, you get a page saying there's a 503.2 Error. 
  • When you attempt to use the Right Click Tools, you will get an error saying that the tools were unable to connect to the Recast Management Server.

Probable Cause

This error usually occurs when too many endpoints are trying to connect to a server. The default limit is 5,000 concurrent connections. If you have more than 5,000 Recast Agents, you might come across this error. 


To increase the concurrent connection limit:

1. Open IIS Manager and on the server node, under Management, select the Configuration Editor.

2. Navigate to system.webServer and select serverRuntime

    NOTE: On older versions of IIS Manager, appConcurrentRequestLimit may be under system.web and httpRuntime.

3. Change the appConcurrentRequestLimit to a higher value. We recommend increasing the value above the current number of Agents in your environment to provide a sufficient buffer, in case you add more later.