敗家貓

一直以來都沒有注意 snapshot 的作用，利用點時間來測看看是否跟文件說的一樣

1、先做個驗證碼
[oracle@c52 dbs]$ md5sum snapcf_rac1.f
2c6acd61155c2deb2d71c3c79f3080a9  snapcf_rac1.f

2、進 rman 做備份 (文件是說每次rman的備份都會先把變化寫到 snapshot裏，再同步controlfile，以避免影響到db效能)
RMAN> backup current controlfile;

3、再查看驗證碼
oracle@c52 dbs]$ md5sum snapcf_rac1.f
3d643f0245f26c97ede2de738873aae6  snapcf_rac1.f

4、從上來看，確時有修改。來試看看如檔案權限不對會如何
[root@c52 dbs]# chown root:root snapcf_rac1.f
[root@c52 dbs]# chmod 000 snapcf_rac1.f
[root@c52 dbs]# ll
----------  1 root   root 18497536 May 19 21:58 snapcf_rac1.f

5、再次做rman
RMAN> backup current controlfile;

Starting backup at 19-MAY-09
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=114 instance=rac1 device type=DISK
channel ORA_DISK_1: starting full datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
including current control file in backup set
channel ORA_DISK_1: starting piece 1 at 19-MAY-09
channel ORA_DISK_1: finished piece 1 at 19-MAY-09
piece handle=/u01/app/oracle/product/11.1.0/db_1/dbs/0okfes3r_1_1 tag=TAG20090519T220026 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:16
Finished backup at 19-MAY-09

RMAN> exit

6、再次查看
-rw-r-----  1 oracle dba 18497536 May 19 22:00 snapcf_rac1.f

結論:沒想到把權限改為都不可讀寫跟owner為root都沒有什影響=.="
最後還是會產生新的snapshot controlfile