DevOps, CI/CD and Automation

We are finishing off an upgrade from forms/reports 6 to 11g, and apart from the normal issues, this has gone very smoothly, but when running some of the 11g reports we are getting the error

Failure of server APACHE bridge:
No backend server available for connection: timed out after 10 seconds or idempotent set to OFF or method not idempotent.

This looks to happen when a running report has not returned the data to the run report window within 5 minutes (happens for both slow queries that fail to return data within that period and also reports where the query is quick, but large numbers of pages are getting produced - some of the reports produce thousands of pages when doing open queries).

Afraid i am not a DBA or administrator so struggling with the weblogic setup stuff (normally just write the reports), but in em the report server is showing the report continuing to run after the run report window has shown the error. Checked the weblogic configuration and cannot see anything different from the documentation, and cannot see any timeout parameters anywhere that are set to 5 minutes (the time it takes to get the error).

All of the report logs in the WLS_REPORTS area look to be fine as far as i can tell, reporting successful completion.

In the web tier OHS component however, messages of type error do appear
*14-May-2013 12:02:04 BST (Error) … HTTP-503 <remote host IP address> - - [14/May/2013:12:02:04 +0100] "POST /reports/rwservlet? HTTP/1.1" 503 253*

*14-May-2013 12:07:04 BST (Error) … OHS-9999 ap_proxy: trying POST /reports/rwservlet at backend host <report server IP address>/9002; got exception 'Backend Server not responding'; state: reading status line or response headers from WLS (wrote? Y read? N); not failing over because method not idempotent, referer: http://<server>:8888/reports/rwservlet/getjobid1515?server=<servername>*

The messages do not appear in the OHS messages log until the failure has happened, but the first has a timestamp that relates to the report start and the second to the time it falls over.

reports that return within the 5 minute timeframe appear to work fine, including when the same report is used with different parameters that reduce the returned data volume

I have tried restarting both the reports server and OHS components (but to be honest only vaugely aware what i am doing here) and this had no effect.

Probably missing something pretty simple, but running out of ideas - can anyone help?

Gary