今天测试的时候纠正了一个错误的印象,一直认为如果当前控制文件被误删除,会导致实例关闭。
而实际上,Oracle并不会结束当前的实例:
SQL> show parameter control_files NAME TYPE VALUE D SQL> host SQL> select * from dual; D SQL> select instance_name, status from v$instance; INSTANCE_NAME STATUS SQL> alter system checkpoint; System altered. SQL> select instance_name, status from v$instance; INSTANCE_NAME STATUS SQL> alter system switch logfile; System altered. SQL> select instance_name, status from v$instance; INSTANCE_NAME STATUS SQL> col name format a50 STATUS NAME IS_ BLOCK_SIZE FILE_SIZE_BLKS SQL> select * from v$controlfile_record_section;
STATUS NAME IS_ BLOCK_SIZE FILE_SIZE_BLKS |
可以看到,删除了一个控制文件之后,数据库照常运行,甚至在发现一个控制文件丢失之后,数据库实例仍然处于打开状态,检查一下alert文件:
Thread 1 advanced to log sequence 21 (LGWR switch) Current log# 3 seq# 21 mem# 0: /u01/oracle/oradata/db01/redo03.log Sun May 24 13:00:58 2009 Errors in file /u01/oracle/diag/rdbms/db01/db01/trace/db01_m002_27935.trc: ORA-00210: cannot open the specified control file ORA-00202: control file: '/u01/oracle/oradata/db01/control02.ctl' ORA-27041: unable to open file Linux Error: 2: No such file or directory Additional information: 3 Sun May 24 13:24:09 2009 Errors in file /u01/oracle/diag/rdbms/db01/db01/trace/db01_m000_27986.trc: ORA-00210: cannot open the specified control file ORA-00202: control file: '/u01/oracle/oradata/db01/control02.ctl' ORA-27041: unable to open file Linux Error: 2: No such file or directory Additional information: 3 Sun May 24 14:01:49 2009 Errors in file /u01/oracle/diag/rdbms/db01/db01/trace/db01_m002_28082.trc: ORA-00210: cannot open the specified control file ORA-00202: control file: '/u01/oracle/oradata/db01/control02.ctl' ORA-27041: unable to open file Linux Error: 2: No such file or directory Additional information: 3 Sun May 24 14:24:59 2009 Errors in file /u01/oracle/diag/rdbms/db01/db01/trace/db01_m000_28132.trc: ORA-00210: cannot open the specified control file ORA-00202: control file: '/u01/oracle/oradata/db01/control02.ctl' ORA-27041: unable to open file Linux Error: 2: No such file or directory Additional information: 3 Sun May 24 14:59:29 2009 Errors in file /u01/oracle/diag/rdbms/db01/db01/trace/db01_m000_28204.trc: ORA-00210: cannot open the specified control file ORA-00202: control file: '/u01/oracle/oradata/db01/control02.ctl' ORA-27041: unable to open file Linux Error: 2: No such file or directory Additional information: 3 |
虽然Oracle认识到一个控制文件出现了异常,但是Oracle并没有关闭当前实例。测试发现,即使删除了所有当前的控制文件,当前实例依然处于打开的状态,并且只有需要访问控制文件的操作会报错,其他操作仍然可以运行。
Oracle既然不会自动关闭,那么万一出现了控制文件误删除的情况,一定不要手工关闭当前的实例,只要实例不关闭,就可以轻松的查询数据库中的数据文件、日志文件等信息来重建控制文件,而一旦关闭了实例,由于缺失控制文件,实例将无法启动,这时候要找到所有控制文件中包含的信息就比较困难了。