We are doing an application upgrade, the application can connect to sql server via OLEDB, but after after 1 minute, get application error message, says: connection failed.
I checked sp_who2, there are about 7 or 8 connections from this application user account, status is sleeping, wait for command.
Is it possible that the 7 or 8 connections are crashed but sql server still show sleeping status? how sql server handler crashed user processes? does sql server have some kind of background process monitor process which check the health of user process and clean out any failed user process? why connection status from sp_who do not have fail status option?
Another possible reason for our issue is that the max size of application's connection pool is too small and application did not close connection properly, so the connections in the pool are not reused as expected. but this is a vendor provided application, the application is installed in other sites without problem and previous version runs well in our site, we just have this problem when we do upgrade, the application should not have the bug like that.
Any help is highly appreciated.