If this setting is enabled then RockSolid will undertake a monitoring "heartbeat" with every SQL Server instance every 30 seconds. During this heart-beat RockSolid will establish a SQL Server connection and execute a simple SQL Server TSQL command to test the instance availability and query processor response.
If SQL Server does not respond then RockSolid will set the state of the instance in RockSolid to down and attempt to raise an Instance Down event.
Example: This instance is currently down and cannot be connected to by the RockSolidAgent. This is indicated by the red cross on the instance icon shown below: