Transactions and locks-setting autocommit

/* drop table  emp; if exists?
CREATE TABLE emp (
	empid Number (5),
	empname varchar2 (m),
	empage number (5)
);
*
/Set autocommit on;  --Set autocommit open show
autocommit;  --View autocommit set
autocommit off;--set autocommit shutdown

examples are as follows:
sql> set autocommit on;
Sql> show autocommit;
Autocommit IMMEDIATE
sql> INSERT INTO EMP
  2  VALUES (
  3  1,
  4  ' CHENZW ',
  5  );

1 lines have been created.

submit completed.
sql> set autocommit off;
Sql> show autocommit;
Autocommit off
sql> inserts into EMP
  2  VALUES (
  3  2,
  4  ' Chenzz ',
  5  );

1 lines have been created.

sql> rollback;

Fallback is complete.

sql> set linesize;
Sql> select * from EMP;

     EMPID empname                                                                                                  Empa
---------------------------------------------------------------------------------- -----------------
         1 CHENZW