SQL & PL/SQL

Hi All,
I am facing some issue with my database. I am not sure how to avoid this.
Database is 10g.

I created a table and inserts some data into that and exit the session with out any commit or rollback and logged in again all the rows I was inserted committed automatically even my set autocommit off. Please help me. This makes my DB as inconsistency.

see the below statements:
=======================
SQL> set autocommit off
SQL> create table a(a number);

Table created.

SQL> insert into a values(1);

1 row created.

SQL> insert into a values(2);

1 row created.

SQL> exit
=======================
Again logged in and checked:-
SQL> select * from a;

A
----------
1
2