In 11g SQL*Plus, when session is terminated, somehow it displays the process ID, SID and Serial#. Not quite sure what is really for? I guess it is for debugging purpose.

10g Client

user @db10w1> select * from dual;
select * from dual
*
ERROR at line 1:
ORA-01012: not logged on

user @db10w1> select * from dual;
select * from dual
*
ERROR at line 1:
ORA-01012: not logged on
Process ID: 0
Session ID: 135 Serial number: 29158