I support an IIS 7.5 web server and I've been having a bit of trouble with my app pools. What I am seeing is every so often, the applications using connections to Oracle databases will stop working and throw a "ORA-12154: TNS:could not resolve the connect identifier specified" error. What's maddening is that nothing has changed on the db server, web server, or inside the app. I've tried a TNS Ping to the database and it connects just fine. Apps in the same app pool using SQL Server databases don't seem to have an issue.
IMPORTANT: If I change the app to belong to a different app pool, it starts working again. If I change it back to the original app pool, the error persists.
What could be happening here? I'm at a loss as to why the issue would just pop up out of the blue and only affect certain pools.