[20190312]视图v$datafile字段OFFLINE_CHANGE#, ONLINE_CHANGE#.txt

--//视图v$datafile存在2个字段OFFLINE_CHANGE#, ONLINE_CHANGE#,想当然会认为数据文件offline时记录scn号的改变.
--//真的吗?通过例子说明:

1.环境:
SYS@book> @ ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

SYS@book> SELECT file#, CHECKPOINT_CHANGE#,CHECKPOINT_TIME,UNRECOVERABLE_CHANGE#,UNRECOVERABLE_TIME,LAST_CHANGE#,LAST_TIME, OFFLINE_CHANGE#, ONLINE_CHANGE#,FIRST_NONLOGGED_SCN,FIRST_NONLOGGED_TIME,status,name FROM v$datafile;
FILE# CHECKPOINT_CHANGE# CHECKPOINT_TIME     UNRECOVERABLE_CHANGE# UNRECOVERABLE_TIME  LAST_CHANGE# LAST_TIME           OFFLINE_CHANGE# ONLINE_CHANGE# FIRST_NONLOGGED_SCN FIRST_NONLOGGED_TIM STATUS  NAME
----- ------------------ ------------------- --------------------- ------------------- ------------ ------------------- --------------- -------------- ------------------- ------------------- ------- --------------------------------------------------
    1        13279958095 2019-03-12 16:40:08                     0                                                                    0              0                   0                     SYSTEM  /mnt/ramdisk/book/system01.dbf
    2        13279958095 2019-03-12 16:40:08                     0                                                                    0    &nb