Does v$session_longops report all the long running sql? Why and when do we use v$session_longops? 

DBA's confuse to use longops view for long running operations due to misunderstanding. This view cannot be used for all long running operations but only for large resource intensive operations like
1)Rman Backup and Restore
2)Parallel Query(Large chunks)
3)Recovery ( Crash and Media )
4)Large Full Table scans
5)Sorting
6)Stats job
7)If the table scan exceeds 10,000 formatted blocks
8)operation is greater than 6 seconds