	1.查询系统当前SCN两条命令

	SQL> select current_scn from v$database;

	SQL> select dbms_flashback.get_system_change_number from dual;

	GET_SYSTEM_CHANGE_NUMBER

	------------------------

1781893

	2.数据库全局-检查点 SCN，在控制文件中。

	SYS@bys1> select dbid,checkpoint_change# from v$database;

	      DBID CHECKPOINT_CHANGE#

	---------- ------------------

	3957527513            1753478

	3.当前数据文件SCN。在控制文件中。即checkpoint scn,表示该数据文件最近一次执行检查点操作时的SCN

	SQL> select name,checkpoint_change# from v$datafile;

	NAME                                               CHECKPOINT_CHANGE#

	-------------------------------------------------- ------------------

	/u01/oradata/bys1/system01.dbf                                1753478

	/u01/oradata/bys1/sysaux01.dbf                                1753478

	SQL> select file#,name,checkpoint_change#,to_char(checkpoint_time,'yyyy-mm-dd hh24:mi:ss') cptime from v$datafile;

	     FILE# NAME                                               CHECKPOINT_CHANGE# CPTIME

	---------- -------------------------------------------------- ------------------ -------------------

	         1 /u01/oradata/bys1/system01.dbf                                1753478 2013-09-11 23:00:52

	         2 /u01/oradata/bys1/sysaux01.dbf                                1753478 2013-09-11 23:00:52

	4.查询数据文件头SCN，在数据文件头

	SQL> select name,checkpoint_change# from v$datafile_header;

	NAME                                     CHECKPOINT_CHANGE#

	---------------------------------------- ------------------

	/u01/app/oracle/oradata/bys001/system01.dbf            1198546

	5.数据文件结束SCN，在控制文件中。

	LAST_CHANGE#，如果数据库非正常关闭值为NULL。正常关闭是关闭时的SCN。

	实例恢复就是在打开数据库时检查此参数确定是否需要恢复。

	数据库OPEN时LAST_CHANGE#也为NULL，因为不确定SCN多少时关闭。

	SQL> select name,last_change# from v$datafile;

	NAME                                     LAST_CHANGE#

	---------------------------------------- ------------

	/u01/app/oracle/oradata/bys001/system01.dbf

	6.日志中所含SCN范围

	SQL> select GROUP#,sequence#,STATUS,FIRST_CHANGE#,to_char(FIRST_TIME,'yyyy/mm/dd:hh24:mi:ss') time from V$log;

	    GROUP#  SEQUENCE# STATUS           FIRST_CHANGE# TIME

	---------- ---------- ---------------- ------------- -------------------

	         1         49 INACTIVE               1713778 2013/09/11:10:10:08

	         2         50 INACTIVE               1744790 2013/09/11:21:34:23

	         3         51 CURRENT                1753478 2013/09/11:23:00:52

ITPub博客

各种scn的查询