Two different ways to retreive the current System Change Number

Use either of the following methods:

SQL> col current_scn format 9999999999999
SQL> select current_scn from v$database;

   CURRENT_SCN
--------------
 6525378448555

SQL> col GET_SYSTEM_CHANGE_NUMBER format 9999999999999
SQL> select dbms_flashback.get_system_change_number from dual;

GET_SYSTEM_CHANGE_NUMBER
------------------------
           6525378448442

Oracle officially recommends tht if your goal is to obtain an SCN from within an application, then you should use the dbms_flashback.get_system_change_number function.