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Oracle备份策略-控制文件和数据文件

我们可以想象,如果控制文件是从备份中恢复的,那么数据库在open过程中又将如何呢?

  首先备份控制文件,打开数据库,增进检查点:

[oracle@jumper eygle]$ cp control01.ctl control01.ctl.bak
[oracle@jumper eygle]$ sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Fri Aug 11 10:46:05 2006
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to an idle instance.
SQL> startup
ORACLE instance started.
Total System Global Area 139531744 bytes
Fixed Size          452064 bytes
Variable Size       121634816 bytes
Database Buffers      16777216 bytes
Redo Buffers         667648 bytes
Database mounted.
Database opened.
SQL> alter system checkpoint;
System altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> exit
Disconnected from Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

  然后恢复旧的控制文件,mount数据库,转储数据文件头:

[oracle@jumper eygle]$ mv control01.ctl control01.ctl.n
[oracle@jumper eygle]$ mv control01.ctl.bak control01.ctl
[oracle@jumper eygle]$ sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Fri Aug 11 10:46:50 2006
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to an idle instance.
SQL> startup mount;
ORACLE instance started.
Total System Global Area 139531744 bytes
Fixed Size          452064 bytes
Variable Size       121634816 bytes
Database Buffers      16777216 bytes
Redo Buffers         667648 bytes
Database mounted.
SQL> alter session set events 'immediate trace name file_hdrs level 10';
Session altered.
SQL> !

  我们看控制文件的信息(选择一个文件):

DATA FILE #4:
 (name #4) /opt/oracle/oradata/eygle/eygle01.dbf
creation size=0 block size=8192 status=0xe head=4 tail=4 dup=1
tablespace 4, index=4 krfil=4 prev_file=0
unrecoverable scn: 0x0000.00000000 01/01/1988 00:00:00

Checkpoint cnt:61 scn: 0x0000.002acb1e 08/11/2006 10:44:38
Stop scn: 0x0000.002acb1e 08/11/2006 10:44:38
Creation Checkpointed at scn: 0x0000.0015078d 06/06/2006 09:41:54

  再看数据文件头信息:

FILE HEADER:
    Software vsn=153092096=0x9200000, Compatibility Vsn=134217728=0x8000000
    Db ID=1407686520=0x53e79778, Db Name='EYGLE'
    Activation ID=0=0x0
    Control Seq=989=0x3dd, File size=1280=0x500
    File Number=4, Blksiz=8192, File Type=3 DATA
Tablespace #4 - EYGLE rel_fn:4
Creation  at  scn: 0x0000.0015078d 06/06/2006 09:41:54
Backup taken at scn: 0x0000.00000000 01/01/1988 00:00:00 thread:0
reset logs count:0x232bee1f scn: 0x0000.0007c781 recovered at 08/11/2006 10:11:26
status:0x0 root dba:0x00000000 chkpt cnt: 64 ctl cnt:63
begin-hot-backup file size: 0
Checkpointed at scn: 0x0000.002acb98 08/11/2006 10:46:24

  我们注意到数据文件的chkpt cnt: 64 要大约控制文件的Checkpoint cnt:61,也就是说控制文件是旧的。

  此时尝试打开数据库就会出现如下错误:

[oracle@jumper udump]$ sqlplus "/ as sysdba"
SQL*Plus: Release 9.2.0.4.0 - Production on Fri Aug 11 10:51:20 2006
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01122: database file 1 failed verification check
ORA-01110: data file 1: '/opt/oracle/oradata/eygle/system01.dbf'
ORA-01207: file is more recent than controlfile - old controlfile

 Oracle告诉我们,控制文件是旧的。此时我们可以通过重建控制文件或者从旧的数据备份开始恢复。