SYSTEM is a database user/schema specific to the Oracle database, NOT the OS.
It is very bad if there are user objects created under SYSTEM schema, and worse if user apps login as the SYSTEM user.
it's much, much worse that you have apps running as SYSTEM - fix that pronto
I have a database running on Windows and none of the sessions are running as Windows SYSTEM. All the background processes are running as ORACLE, and my client session is running as my logged in user.
Excluding background sessions doesn't seem to be the reason for the osuser <> 'SYSTEM' filter.
I'm not familiar enough with developing apps for windows to know how bad it is that things are running as Windows SYSTEM, but there are a lot of non-windows processes running as SYSTEM on my laptop. There are two oracle services (OracleMTSRecoveryService and OracleOraDB11g_Home1ClrAgent) both running as Windows SYSTEM.
I'm the DBA not the developer, so I can't control what accounts the application runs under on their servers, but I've passed that information on to them so they can check it out. Though I think in this particular case where I noticed this it's a COTS product being used.
Anyway, I still don't understand why that filter exists to exclude OS users of "SYSTEM". It may be bad practice for an application to connect from the Windows SYSTEM account, but that doesn't explain why SQL Developer is filtering them out from Monitor Sessions.
And Gaz in Oz, this isn't the Oracle SYSTEM user/schema at issue. It's the "osuser" column from v$session that is being filtered, which is the user on the connecting session's OS.
Ok i read 'system' and thought, database account - system.
There's no reason for us to filter out sessions based on the OS user name that I know of, i'll file a bug.
some apps that connect to the DB from the Windows SYSTEM OSUser account and it is hiding important sessions I know are there.
(they do show up in TOAD 12.6 session browser as long as their filter "Exclude NULL and SYSTEM OS Users" is off)
Amazing that I hunted this down on internet and the amazing Jeff Smith of Oracle just commented on in about 10 minutes ago!