【备份恢复】之scn续

SQL> startup mount
ORACLE instance started.

Total System Global Area    238530560 bytes
Fixed Size                                    1335724 bytes
Variable Size                         159387220 bytes
Database Buffers                     75497472 bytes
Redo Buffers                                2310144 bytes
Database mounted.
SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
                        880846

SQL> select checkpoint_change# from v$datafile;

CHECKPOINT_CHANGE#
------------------
                        880846
                        880846
                        880846
                        880846

SQL> select last_change# from v$datafile;

LAST_CHANGE#
------------                                        ------终止scn为null

SQL> select checkpoint_change# from v$datafile_header;

CHECKPOINT_CHANGE#
------------------
                        880846
                        880846
                        880846
                        880846



数据库开启前比较v$datafile_header.checkpoint_change#v$database.checkpoint_change#
v$datafile_header.checkpoint_change#和v$datafile.last_change#此时启动scn与终止scn不同，那么数据库需要实例恢复。  

SQL> alter database open;

Database altered.

SQL> select checkpoint_change# from v$database;

CHECKPOINT_CHANGE#
------------------
                        905596

SQL> select checkpoint_change# from v$datafile;

CHECKPOINT_CHANGE#
------------------
                        905596
                        905596
                        905596
                        905596

SQL> select last_change# from v$datafile;

LAST_CHANGE#
------------

SQL> select checkpoint_change# from v$datafile_header;

CHECKPOINT_CHANGE#
------------------
                        905596
                        905596
                        905596
                        905596
此时数据库smon进程做了实例恢复，所谓实例恢复就是指内存和进程，