I'm trying to diagnose what is causing regular crashes and hangs in one of our database applications. Operating system is windows server 2003, database server is SQL server enterprise 2005.
We recieve a large number of errors like this prior to the crash/hang.
Error: OLEDB returned result 80004005. Description: E_FAIL. Unspecified error
I've spoken to the software vendor and they believe this is being caused either by either excessive load on the SQL server or by a loss of connectivity with the SQL server.
I do not believe this is a load issue - if anything it appears worse overnight when there is less load on the SQL server (it's possibly an idling issue?). Connectivity is a possibility however other databases on the server do not experience issues, and another application accessing the database is not reporting any issues (although it may be more fault tolerant).
Running tests on our test system I can occasionally replicate this issue by blocking the SQL server port via windows firewall for ~20 seconds and then reenabling - sometimes it results in the same behaviour, sometimes the application recovers. I've written a utility to try and connect to the database every second to check for connectivity, however it didn't show any loss of connectivity.
What next steps can I take to prove/disprove the SQL server connectivity is good?