Home Database Mysql Tutorial 恢复被误删除的oracle数据文件(一)

恢复被误删除的oracle数据文件(一)

Jun 07, 2016 pm 05:37 PM
Database recovery

在生产环境,总会发生数据库的数据文件被误删除的事情,如SA不懂得数据库,数据库的在线日志为redo01.log,还是cp备份后删除的,让人哭笑不得,数据文件命名为无

       在生产环境,总会发生数据库的数据文件被误删除的事情,如SA不懂得数据库,数据库的在线日志为redo01.log,还是cp备份后删除的,让人哭笑不得,数据文件命名为无dbf后缀等,都容易被误删除
       在操作系统层面被误rm的,如果及时发现,还是可以挽救的,下面举例说明下:

1、查询数据库版本和是否归档模式

SQL> select * from v$version; BANNER -------------------------------------------------------------------------------- Oracle Database 11g Enterprise Edition Release 11.1.0.7.0 - 64bit Production PL/SQL Release 11.1.0.7.0 - Production CORE 11.1.0.7.0 Production TNS for Linux: Version 11.1.0.7.0 - Production NLSRTL Version 11.1.0.7.0 - Production SQL> archive log list; Database log mode Archive Mode Automatic archival Enabled Archive destination /archivelog Oldest online log sequence 1 Next log sequence to archive 1 Current log sequence 1

2、fly用户创建表fly,fly表的记录数为1128432

SQL> conn fly/fly Connected. SQL> create table fly as select * from dba_objects; Table created. SQL> insert into fly select * from fly; 70527 rows created. SQL> / 141054 rows created. SQL> / 282108 rows created. SQL> / 564216 rows created. SQL> commit; Commit complete. SQL> select count(*) from fly; COUNT(*) ---------- 1128432

3、查看fly用户默认表空间的数据文件,用操作系统命令rm删除fly用户默认表空间下的所有数据文件

SQL> conn sys/oracle as sysdba Connected. SQL> select default_tablespace from dba_users where username='FLY'; DEFAULT_TABLESPACE ------------------------------ USERS SQL> col file_name format a80 SQL> set linesize 200 SQL> select file_name from dba_data_files where tablespace_name='USERS'; FILE_NAME -------------------------------------------------------------------------------- /home/oracle/oradata/fly/datafile/users02.dbf /home/oracle/oradata/fly/datafile/user03.dbf SQL> host rm /home/oracle/oradata/fly/datafile/users02.dbf SQL> host rm /home/oracle/oradata/fly/datafile/user03.dbf

4、在fly用户下创建表fly007,报错了,注意及时多执行几次创建表的SQL语句,这边都只显示user02.dbf数据文件不存在了,接下来的恢复中,我们肯定要考虑到到底被误删除了几个数据文件

SQL> conn fly/fly Connected. SQL> create table fly007 as select * from dba_objects; create table fly007 as select * from dba_objects * ERROR at line 1: ORA-01116: error in opening database file 20 ORA-01110: data file 20: '/home/oracle/oradata/fly/datafile/users02.dbf' ORA-27041: unable to open file Linux-x86_64 Error: 2: No such file or directory Additional information: 3

5、查看该文件是否仍旧被某些进程打开着

fly007:~ # lsof | grep /home/oracle/oradata/fly/datafile/users02.dbf oracle 22297 oracle 32uW REG 8,2 209723392 1410008 /home/oracle/oradata/fly/datafile/users02.dbf (deleted) oracle 22301 oracle 42u REG 8,2 209723392 1410008 /home/oracle/oradata/fly/datafile/users02.dbf (deleted) oracle 22309 oracle 30u REG 8,2 209723392 1410008 /home/oracle/oradata/fly/datafile/users02.dbf (deleted) oracle 22317 oracle 32u REG 8,2 209723392 1410008 /home/oracle/oradata/fly/datafile/users02.dbf (deleted)

6、数据库的dbwr进程会打开所有的数据文件,包括控制文件,查看dbwr进程的PID为22297

fly007:~ # ps -ef | grep dbw0 | grep -v grep oracle 22297 1 0 21:21 ? 00:00:00 ora_dbw0_fly

 

误删除数据文件恢复原理
        当进程打开了某个文件时,只要该进程仍旧保持打开该文件,即使将该文件删除了,该进程仍然可以向打开该文件时提供给它的文件描述符进行读取和写入操作。在/proc 目录下,包含了反映内核和进程树的各种文件。/proc目录挂载的是在内存中所映射的一块区域,所以这些文件和目录并不存在于磁盘中,因此当我们对这些文件进行读取和写入时,实际上是在从内存中获取相关信息。大多数与lsof 相关的信息都存储于以进程的PID 命名的目录中,即/proc/1116 中包含的是PID 为1116的进程的信息。每个进程目录中存在着各种文件,它们可以使得应用程序简单地了解进程的内存空间、文件描述符列表、指向磁盘上的文件的符号链接和其他系统信息。lsof 程序使用该信息和其他关于内核内部状态的信息来产生其输出。所以lsof 可以显示进程的文件描述符和相关的文件名等信息。也就是我们通过访问进程的文件描述符可以找到该文件的相关信息。
        当系统中的某个文件被意外的删除了,只要这个时候系统中还有进程正在访问该文件,那么我们就可以通过lsof从/proc目录下恢复该文件的内容

 

7、进入到dbwr进程的fd(文件描述符)目录下,需要确定被删除的数据文件是不是只有一个user02.dbf,结果发现不是的,10,25,32为fd(文件描述符)

fly007:~ # cd /proc/22297/fd fly007:/proc/22297/fd # ls -l | grep delete lrwx------ 1 oracle oinstall 64 Dec 6 21:26 10 -> /home/oracle/product/11g/db/dbs/lkinstfly (deleted) lrwx------ 1 oracle oinstall 64 Dec 6 21:26 25 -> /home/oracle/oradata/fly/datafile/user03.dbf (deleted) lrwx------ 1 oracle oinstall 64 Dec 6 21:26 32 -> /home/oracle/oradata/fly/datafile/users02.dbf (deleted) fly007:/proc/22297/fd # ls -l /home/oracle/oradata/fly/datafile/user03.dbf /bin/ls: /home/oracle/oradata/fly/datafile/user03.dbf: No such file or directory
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