Online DDL Modifications In Oracle

Yesterday, I have post Changing Data Type of Non Empty Column In Oracle
Tonguc made me to investigate with DBMS_REDEFINITION supplied package that you make online DDL modifications with his post. I made a simple example:
Connected to Oracle Database 10g Express Edition Release 10.2.0.1.0
Connected as SYS

SQL> create table z( i number);

Table created

SQL> create table zzz( i varchar2(12));

Table created

SQL> INSERT INTO z VALUES( 4);

1 row inserted

SQL> commit;

Commit complete

SQL> exec dbms_redefinition.start_redef_table(user,'z','zzz','i i');

begin dbms_redefinition.start_redef_table(user,'z','zzz','i i'); end;

ORA-12087: online redefinition not allowed on tables owned by "SYS"
ORA-06512: at "SYS.DBMS_REDEFINITION", line 50
ORA-06512: at "SYS.DBMS_REDEFINITION", line 1343
ORA-06512: at line 1

SQL> drop table z;

Table dropped

SQL> drop table zzz;

Table dropped

SQL> grant execute on dbms_redefinition to hr;

Grant succeeded

SQL> grant CREATE ANY TABLE, ALTER ANY TABLE, DROP ANY TABLE, LOCK ANY TABLE, SELECT ANY TABLE to hr;

Grant succeeded

SQL> conn hr/hr
Connected to Oracle Database 10g Express Edition Release 10.2.0.1.0
Connected as hr

SQL> create table z( i number);

Table created

SQL> INSERT INTO z VALUES( 4);

1 row inserted

SQL> commit;

Commit complete

SQL> create table zzz( i varchar2(12));

Table created


SQL> exec dbms_redefinition.start_redef_table(user,'z','zzz','i i');

begin dbms_redefinition.start_redef_table(user,'z','zzz','i i'); end;

ORA-12089: cannot online redefine table "HR"."Z" with no primary key
ORA-06512: at "SYS.DBMS_REDEFINITION", line 50
ORA-06512: at "SYS.DBMS_REDEFINITION", line 1343
ORA-06512: at line 1

SQL> exec dbms_redefinition.start_redef_table(user,'z','zzz','i i',2);

begin dbms_redefinition.start_redef_table(user,'z','zzz','i i',2); end;

ORA-42016: shape of interim table does not match specified column mapping
ORA-06512: at "SYS.DBMS_REDEFINITION", line 50
ORA-06512: at "SYS.DBMS_REDEFINITION", line 1343
ORA-06512: at line 1

SQL> exec dbms_redefinition.start_redef_table(user,'z','zzz','to_char(i) i',2);

PL/SQL procedure successfully completed

SQL> INSERT INTO z VALUES( 41);

1 row inserted

SQL> INSERT INTO z VALUES( 411);

1 row inserted

SQL> commit;

Commit complete

SQL> exec dbms_redefinition.sync_interim_table(user,'z','zzz');

PL/SQL procedure successfully completed

SQL> exec dbms_redefinition.finish_redef_table(user,'z','zzz');

PL/SQL procedure successfully completed

SQL> desc z;
Name Type Nullable Default Comments
---- ------------ -------- ------- --------
I VARCHAR2(12) Y

SQL> SELECT * FROM z;

I
------------
4
41
411

SQL>