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oracle snapcf_.f/ SNAPSHOT CONTROLFILE 什么作用？

在$ORACLE_HOME/dbs/下有个snapcf_sid.f文件，也就是在rman 中CONFIGURE SNAPSHOT CONTROLFILE NAME TO ‘xxxx’ 的文件，据我个人理解，它就是一个控制文件的快照，rman同步catalog或备份控制文件时会自动更新这个文件，在rman 的restore controlfile from autobackup时需要，可以用来恢复控制文件。

在metalink 也有介绍，

2.1 Snapshot Controlfile

When RMAN needs to resynchronize from a read-consistent version of the control file, it creates a temporary snapshot control file. The defaultname for the snapshot control file is port-specific. Use the set snapshot controlfile name command to change the name of the snapshot control file; subsequent snapshot control files that RMAN creates use the name specified in the command.

结论是：
1.SNAPSHOT CONTROLFILE 不能直接copy成control file，如果数据库已经shutdown
2.可以通过rman，将SNAPSHOT CONTROLFILE 恢复成控制文件
3.如果数据库没有shutdown，可以直接copy SNAPSHOT CONTROLFILE 成控制文件，但仍需要恢复（因为他是旧的）

下面是我的测试步骤：
—————————————
查看snapshot controlfile的备份设置:

RMAN> SHOW SNAPSHOT CONTROLFILE NAME;

RMAN configuration parameters are:
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/u01/ora9a/product/9.2/dbs/snapcf_tt9a.f'; # default

RMAN>

下面模拟控制文件丢失的恢复

$ ls
control01.ctl cwmlite01.dbf indx01.dbf redo02.log temp01.dbf users01.dbf
control02.ctl drsys01.dbf odm01.dbf redo03.log tools01.dbf xdb01.dbf
control03.ctl example01.dbf redo01.log system01.dbf undotbs01.dbf
$ rm cont* --删除控制文件
$ ls
cwmlite01.dbf example01.dbf odm01.dbf redo02.log system01.dbf tools01.dbf users01.dbf
drsys01.dbf indx01.dbf redo01.log redo03.log temp01.dbf undotbs01.dbf xdb01.dbf
$

在控制文件被删除后，数据库还能正常操作：

SQL> insert into test(no) values(4);

1 row created.

SQL> commit;

Commit complete.

SQL> alter system switch logfile;

System altered.

SQL> alter system checkpoint;

System altered.

SQL> /

System altered.

SQL>
SQL> select no,to_char(vdate,'yyyy-mm-dd hh24:mi:ss') from test;

NO TO_CHAR(VDATE,'YYYY-MM-DDHH24:MI:SS')
---------- ---------------------------------------------------------
1 2009-02-24 10:16:09
2 2009-02-24 10:25:30
3 2009-02-24 10:26:56
4 2009-02-24 10:30:59

SQL>

重新启动数据库：

SQL> connect /as sysdba
Connected.
SQL> shutdown immediate
ORA-00210: cannot open the specified controlfile
ORA-00202: controlfile: '/u01/ora9a/oradata/tt9a/control01.ctl'
ORA-27041: unable to open file
IBM AIX RISC System/6000 Error: 2: No such file or directory
Additional information: 3

没有了控制文件了，shutdown immediate出错

SQL>
SQL> shutdown abort;
ORACLE instance shut down.
SQL> startup
ORACLE instance started.

Total System Global Area 320569400 bytes
Fixed Size 741432 bytes
Variable Size 285212672 bytes
Database Buffers 33554432 bytes
Redo Buffers 1060864 bytes
ORA-00205: error in identifying controlfile, check alert log for more info

SQL>

没有控制文件，数据库不能mount，现在把SNAPSHOT CONTROLFILE copy到对应目录

$ cp /u01/ora9a/product/9.2/dbs/snapcf_tt9a.f /u01/ora9a/oradata/tt9a/control01.ctl
$ cp /u01/ora9a/oradata/tt9a/control01.ctl /u01/ora9a/oradata/tt9a/control0t.ctl
$ cp /u01/ora9a/oradata/tt9a/control01.ctl /u01/ora9a/oradata/tt9a/control03.ctl
$ ls -lrt /u01/ora9a/oradata/tt9a/contr*
-rw-r----- 1 ora9a dba 1531904 Feb 24 10:36 /u01/ora9a/oradata/tt9a/control01.ctl
-rw-r----- 1 ora9a dba 1531904 Feb 24 10:36 /u01/ora9a/oradata/tt9a/control0t.ctl
-rw-r----- 1 ora9a dba 1531904 Feb 24 10:36 /u01/ora9a/oradata/tt9a/control03.ctl
$
SQL> startup
ORACLE instance started.

Total System Global Area 320569400 bytes
Fixed Size 741432 bytes
Variable Size 285212672 bytes
Database Buffers 33554432 bytes
Redo Buffers 1060864 bytes
ORA-00205: error in identifying controlfile, check alert log for more info

照样不能mount数据库
—————————————-
尝试用rman恢复控制文件:

$ rman target /

Recovery Manager: Release 9.2.0.1.0 - 64bit Production

Copyright (c) 1995, 2002, Oracle Corporation. All rights reserved.

connected to target database (not started)

RMAN> startup nomount;

Oracle instance started

Total System Global Area 320569400 bytes

Fixed Size 741432 bytes
Variable Size 285212672 bytes
Database Buffers 33554432 bytes
Redo Buffers 1060864 bytes

RMAN> restore controlfile from '/u01/ora9a/product/9.2/dbs/snapcf_tt9a.f';

Starting restore at 24-FEB-09

using target database controlfile instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=13 devtype=DISK
channel ORA_DISK_1: copied controlfile copy
replicating controlfile
input filename=/u01/ora9a/oradata/tt9a/control01.ctl
output filename=/u01/ora9a/oradata/tt9a/control02.ctl
output filename=/u01/ora9a/oradata/tt9a/control03.ctl
Finished restore at 24-FEB-09

RMAN> alter database mount;

database mounted

RMAN>

ok,用rman可以进行恢复，让数据mount起来
恢复数据库

RMAN> recover database;

Starting recover at 24-FEB-09
using channel ORA_DISK_1

starting media recovery

archive log thread 1 sequence 1 is already on disk as file /u01/ora9a/oradata/tt9a/redo01.log
archive log thread 1 sequence 2 is already on disk as file /u01/ora9a/oradata/tt9a/redo02.log
archive log thread 1 sequence 3 is already on disk as file /u01/ora9a/oradata/tt9a/redo03.log
archive log filename=/u01/ora9a/oradata/tt9a/redo01.log thread=1 sequence=0
archive log filename=/u01/ora9a/oradata/tt9a/redo02.log thread=1 sequence=2
archive log filename=/u01/ora9a/oradata/tt9a/redo03.log thread=1 sequence=3
media recovery complete
Finished recover at 24-FEB-09

RMAN> alter database open;

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of alter db command at 02/24/2009 10:47:36
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open

RMAN> alter database open resetlogs;

database opened

RMAN>

查看先前insert的数据：

SQL> select no,to_char(vdate,'yyyy-mm-dd hh24:mi:ss') from test;

NO TO_CHAR(VDATE,'YYYY-MM-DDHH24:MI:SS')
---------- ---------------------------------------------------------
1 2009-02-24 10:16:09
2 2009-02-24 10:25:30
3 2009-02-24 10:26:56
4 2009-02-24 10:30:59

SQL>

数据仍在，恢复成功!

=============================
下面仍是在数据库正常运行情况下，将控制文件删除，仍测试直接copy SNAPSHOT CONTROLFILE 的恢复方式：

SQL> insert into test(no) values(5);
1 row created.

SQL> commit;
Commit complete.

SQL>
SQL> !
$ pwd
/u01/ora9a/oradata/tt9a
$ ls
control01.ctl control0t.ctl example01.dbf redo01.log system01.dbf undotbs01.dbf
control02.ctl cwmlite01.dbf indx01.dbf redo02.log temp01.dbf users01.dbf
control03.ctl drsys01.dbf odm01.dbf redo03.log tools01.dbf xdb01.dbf
$ rm contr*
$ ls
cwmlite01.dbf example01.dbf odm01.dbf redo02.log system01.dbf tools01.dbf users01.dbf
drsys01.dbf indx01.dbf redo01.log redo03.log temp01.dbf undotbs01.dbf xdb01.dbf
$
$ exit

SQL> select * from v$controlfile;

STATUS
---------------------
NAME
--------------------------------------------------------------------------------

/u01/ora9a/oradata/tt9a/control01.ctl
/u01/ora9a/oradata/tt9a/control02.ctl
/u01/ora9a/oradata/tt9a/control03.ctl
SQL> select dbid from v$database;
select dbid from v$database
*
ERROR at line 1:
ORA-00210: cannot open the specified controlfile
ORA-00202: controlfile: '/u01/ora9a/oradata/tt9a/control01.ctl'
ORA-27041: unable to open file
IBM AIX RISC System/6000 Error: 2: No such file or directory
Additional information: 3

SQL>

没有控制文件，查询失败
现在将SNAPSHOT CONTROLFILE copy到对应目录，尝试直接恢复成控制文件:

SQL> !
$ pwd
/u01/ora9a/oradata/tt9a
$ cp /u01/ora9a/product/9.2/dbs/snapcf_tt9a.f control01.ctl
$ cp control01.ctl control02.ctl
$ cp control01.ctl control03.ctl
$ ls -lrt cont*
-rw-r----- 1 ora9a dba 1531904 Feb 24 10:55 control01.ctl
-rw-r----- 1 ora9a dba 1531904 Feb 24 10:55 control02.ctl
-rw-r----- 1 ora9a dba 1531904 Feb 24 10:55 control03.ctl
$

注意，此时不要起停数据库，否则这样恢复的控制文件仍不可用
尝试查询control file信息

SQL> select dbid from v$database;

DBID
----------
3459515476

SQL>

ok,成功
查询数据文件头信息

SQL> select CHECKPOINT_CHANGE# from v$datafile_header;
select CHECKPOINT_CHANGE# from v$datafile_header
*
ERROR at line 1:
ORA-00600: internal error code, arguments: [2170], [], [], [], [], [], [], []

SQL>

失败
现在重新启动数据库，看看是否可以到mount状态：

SQL> shutdown immediate
ORA-00600: internal error code, arguments: [kccchb_1], [356], [353], [0], [353], [0], [], []
SQL> shutdown abort;
ORACLE instance shut down.
SQL>
SQL> startup
ORACLE instance started.

Total System Global Area 320569400 bytes
Fixed Size 741432 bytes
Variable Size 285212672 bytes
Database Buffers 33554432 bytes
Redo Buffers 1060864 bytes
Database mounted.
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
SQL>

ok，此时数据库可以mount起来了

SQL>
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
SQL> alter database open resetlogs;
alter database open resetlogs
*
ERROR at line 1:
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: '/u01/ora9a/oradata/tt9a/system01.dbf'

提示需要恢复

SQL> recover database using backup controlfile;
ORA-00279: change 349227 generated at 02/24/2009 10:49:58 needed for thread 1
ORA-00289: suggestion : /u01/arch/1_1.dbf
ORA-00280: change 349227 for thread 1 is in sequence #1
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
AUTO
ORA-00328: archived log ends at change 347581, need later change 349227
ORA-00334: archived log: '/u01/arch/1_1.dbf'
SQL> recover database using backup controlfile;
ORA-00279: change 349227 generated at 02/24/2009 10:49:58 needed for thread 1
ORA-00289: suggestion : /u01/arch/1_1.dbf
ORA-00280: change 349227 for thread 1 is in sequence #1
Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
/u01/ora9a/oradata/tt9a/redo01.log
Log applied.
Media recovery complete.

SQL> alter database open resetlogs;

Database altered.

SQL>

恢复成功

SQL> select no,to_char(vdate,'yyyy-mm-dd hh24:mi:ss') from test order by vdate;

NO TO_CHAR(VDATE,'YYYY-MM-DDHH24:MI:SS')
---------- ---------------------------------------------------------
1 2009-02-24 10:16:09
2 2009-02-24 10:25:30
3 2009-02-24 10:26:56
4 2009-02-24 10:30:59
5 2009-02-24 10:51:01

SQL>

ok,新插入的数据也在。

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