Oracle viewing data file header SCN information

Oracle Database view data file header SCN Number

select a.name,a.checkpoint_change# "start_SCN",
b.checkpoint_change# "last_SCN"
from v$datafile_header a, v$datafile b
where a.file#=b.file#;

NAME                                           start_SCN   last_SCN
--------------------------------------------- ---------- ----------
D:\CCDATA\NEWHIS\SYSTEM01.DBF                 3295957260 3311098792
D:\CCDATA\NEWHIS\SYSAUX01.DBF                 3295957262 3311098792
D:\CCDATA\NEWHIS\UNDOTBS01.DBF                3295957279 3311098792
D:\CCDATA\NEWHIS\USERS01.DBF                  3295957260 3311098792
D:\CCDATA\NEWHIS\HTHIS.ORA                    3295957262 3311098792
D:\CCDATA\NEWHIS\XX.ORA                       3295957261 3311098792
D:\CCDATA\NEWHIS\HTEMR.ORA                    3295957261 3311098792
D:\CCDATA\NEWHIS\HTHIS1.ORA                    3295957261 3311098792
D:\CCDATA\NEWHIS\HTHIS2.ORA                   3295957261 3311098792
D:\CCDATA\NEWHIS\HTHIS3.ORA                   3295957261 3311098792
D:\CCDATA\NEWHIS\HTHIS4.ORA                   3295957279 3311098792

NAME                                           start_SCN   last_SCN
--------------------------------------------- ---------- ----------
D:\CCDATA\NEWHIS\HTHIS5.ORA                   3295957262 3311098792
D:\CCDATA\NEWHIS\HTHIS6.ORA                   3295957279 3311098792
D:\CCDATA\NEWHIS\HTHIS7.ORA                   3295957262 3311098792
D:\CCDATA\NEWHIS\HTHIS8.ORA                   3295957279 3311098792
D:\CCDATA\NEWHIS\HTHIS9.ORA                   3295957261 3311098792
D:\CCDATA\NEWHIS\HTHIS10.ORA                  3295957260 3311098792
D:\CCDATA\NEWHIS\HTHIS11.ORA                  3295957260 3311098792
D:\CCDATA\NEWHIS\HTHIS12.ORA                  3295957262 3311098792
D:\CCDATA\NEWHIS\SYSTEM02.ORA                 3295957279 3311098792

 Have chosen 20 That's ok .