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043-157

原创 Linux操作系统 作者:jbymy2000 时间:2012-03-10 09:29:25 0 删除 编辑
157. The loss of the control file forced you to re-create the control
file. After re-creating it and opening the database, you find that s
ome of the data files are named as MISSING nnnnn, where nnnnn is a fi
ve-digit number starting with 0. What could be the possible reason?
A. These are the data files that are corrupted.
B. There is no SYSAUX tablespace in your database
C. There is a read-only tablespace in your database.
D. These are the data files that cannot be recovered.
Answer: C
Read-only files should not be listed in the CREATE CONTROLFILE
statement so that recovery can skip these files.
No recovery is required for read-only datafiles unless you restored
backups of these files from a time when the datafiles were read/write.
After you create a new control file and attempt to mount and open the
database, the database performs a data dictionary check against the files
listed in the control file. For each file that is not listed in the CREATE
CONTROLFILE statement but is present in the data dictionary, an entry is
created for them in the control file. These files are named as MISSINGnnnnn,
where nnnnn is a five digit number starting with 0.After the database is
open, rename the read-only files to their correct filenames by executing
the ALTER DATABASE RENAME FILE statement for all the files whose name
is prefixed with MISSING.
All the restrictions related to read-only files in CREATE CONTROLFILE
statements also apply to offline normal tablespaces, except that you need
to bring the tablespace online after the database is open. You should leave
out tempfiles from the CREATE
CONTROLFILE statement and add them after database open.
只读文件是不记录在Create ControlFile 这个“救命”语句里面的,原因
是没有必要对这些文件进行恢复操作,但是,数据字典里面是有这些read-only
表空间的记录的,当用一个新的 control file 打开数据库的时候,Oracle 会
检查新 control file 中的文件列表和数据字典里面的文件列表对比,结果在新
control file 中找不到,于是就会将这些文件命名为 MISSINGnnnnn (n 是数字,
以0 为开头)。

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