ODP.NET

I am trying to execute a long-running Oracle procedure from .NET. The procedure takes about three hours to finish. Ideally, I would like the user to be able to close the browser and come back later to check on the results. The problem is that the connection to Oracle is lost after exactly an hour (whether or not the browser is closed). As you would expect, the procedure finishes when run from SQL Plus. Strangely enough, it also runs to completion if I set a breakpoint in my .NET code after the procedure is invoked (I kick off two asynchronous threads, one of which executes the procedure. I set a breakpoint on the second).

My connection string:
data source= (DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=server123)(PORT=1521)))(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=SID_abc)))

Some relevant lines from web.config:
<sessionState mode="InProc" cookieless="false" timeout="3000" stateNetworkTimeout="72000"/>
<httpRuntime executionTimeout="18000" maxRequestLength="2097151" />

Any thoughts as to why the connection would be lost after an hour, and what I can do to maintain the connection till the procedure finishes?

Thanks,

Tom