Checking oracle sid and database name

I presume select user from dual; should give you the current user

and select sys_context('userenv','instance_name') from dual; the name of the instance

I believe you can get SID as SELECT sys_context('USERENV', 'SID') FROM DUAL; (can't to check this now)

http://stackoverflow.com/questions/6288122/checking-oracle-sid-and-database-name