SQL> select  *
  2    from  v$version
  3  /

BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Prod
PL/SQL Release 10.2.0.4.0 - Production
CORE    10.2.0.4.0      Production
TNS for 32-bit Windows: Version 10.2.0.4.0 - Production
NLSRTL Version 10.2.0.4.0 - Production

Elapsed: 00:00:01.29

SQL> create table tbl(n number);

Table created.

Elapsed: 00:00:00.29
SQL> create sequence s;

Sequence created.

SQL> insert
  2    into tbl
  3    select  s.nextval
  4      from  dual
  5      connect by level <= 1000000
  6  /

1000000 rows created.

Elapsed: 00:00:19.71

SQL> create table tbl_guid(n raw(16))
  2  /

Table created.

Elapsed: 00:00:00.07
SQL> insert
  2    into tbl_guid
  3    select  sys_guid()
  4      from  dual
  5      connect by level <= 1000000
  6  /

1000000 rows created.

Elapsed: 00:00:40.23

SQL> create sequence s cache 100
  2  /

Sequence created.

Elapsed: 00:00:00.00
SQL> insert
  2    into tbl
  3    select  s.nextval
  4      from  dual
  5      connect by level <= 1000000
  6  /

1000000 rows created.

Elapsed: 00:00:05.40
SQL> 

SQL> select * from v$version order by 1;

BANNER
----------------------------------------------------------------
CORE    10.2.0.1.0      Production
NLSRTL Version 10.2.0.1.0 - Production
Oracle Database 10g Express Edition Release 10.2.0.1.0 - Product
PL/SQL Release 10.2.0.1.0 - Production
TNS for 32-bit Windows: Version 10.2.0.1.0 - Production

SQL> select dbms_utility.port_string from dual;

PORT_STRING
--------------------------------------------------------------------------------
IBMPC/WIN_NT-8.1.0

SQL> BEGIN
  2  FOR indx IN 1 .. 5
  3  LOOP
  4  DBMS_OUTPUT.put_line ( SYS_GUID );
  5  END LOOP;
  6  END;
  7  /
8295E8290E5D4A6AAE72ACB0E0099BAE
AC073A39926C46DFB487A111859C2EB8
2D90C80B0EE7431AB07EDBBD4D0393F6
9F3B8D8BCDA249648ECFB3F6707C20AE
A395082816FE4EFB9833B9EA5E163012

PL/SQL procedure successfully completed.

SQL>

SQL> select * from v$version order by 1;

BANNER
--------------------------------------------------------------------------------
CORE    11.2.0.1.0      Production
NLSRTL Version 11.2.0.1.0 - Production
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
TNS for Solaris: Version 11.2.0.1.0 - Production

SQL> select dbms_utility.port_string from dual;

PORT_STRING
--------------------------------------------------------------------------------
SVR4-be-64bit-8.1.0

SQL> BEGIN
  2  FOR indx IN 1 .. 5
  3  LOOP
  4  DBMS_OUTPUT.put_line ( SYS_GUID );
  5  END LOOP;
  6  END;
  7  /
C0319B33F73A4F63E0440003BA60882B
C0319B33F73B4F63E0440003BA60882B
C0319B33F73C4F63E0440003BA60882B
C0319B33F73D4F63E0440003BA60882B
C0319B33F73E4F63E0440003BA60882B

PL/SQL procedure successfully completed.

SQL>