In the SQL*Plus session below, I connect as SYS to an Oracle 10 database. Then I show that there is only one user logged on as SYS i.e. me. I note the sid and serial# and try to use them to kill my current session. Oracle does not allow this and displays an ORA-00027:
SQL> conn / as sysdba
SQL> show user
USER is "SYS"
SQL> select sid, serial# from v$session
2 where username = 'SYS'
SQL> alter system kill session '159,5';
alter system kill session '159,5'
ERROR at line 1:
ORA-00027: cannot kill current session
A colleague recently bought a copy of the book advertised below. It explains ORA-00027 on page 729. I had a good look at the book today and can thoroughly recommend it. I will be featuring worked examples from it in due course: