环境模拟
删除状态为active的联机日志，然后强行关闭数据库
处理过程
SQL> startup
ORACLE instance started.
Total System Global Area 167772160 bytes
Fixed Size 1260720 bytes
Variable Size 142607184 bytes
Database Buffers 16777216 bytes
Redo Buffers 7127040 bytes
Database mounted.
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: ‘/u01/oradata/xienfei/redo01.log’
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
Alert.log 日志中错误
Wed Aug 24 00:26:33 2011
Errors in file /u01/admin/xienfei/udump/xff_ora_9186.trc:
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: ‘/u01/oradata/xienfei/redo01.log’
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
xff_ora_9186.trc文件中错误
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: ‘/u01/oradata/xienfei/redo01.log’
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
查询当前日志组状态
SQL> select a.group#,a.status,b.member from v$log a,v$logfile b where a.group#=b.group#;
GROUP# STATUS MEMBER
———- —————- ———————————————
1 CURRENT /u01/oradata/xienfei/redo01.log
3 INACTIVE /u01/oradata/xienfei/redo03.log
2 ACTIVE /u01/oradata/xienfei/redo02.log
尝试删除redo日志
SQL> alter database drop logfile group 1;
alter database drop logfile group 1
*
ERROR at line 1:
ORA-01623: log 1 is current log for instance xff (thread 1) – cannot drop
ORA-00312: online log 1 thread 1: ‘/u01/oradata/xienfei/redo01.log’
发现是当前日志不能被删除，尝试切换日志
SQL> alter system switch logfile;
alter system switch logfile
*
ERROR at line 1:
ORA-01109: database not open
在数据库未打开状态，不能切换日志，只能尝试清空日志
SQL> alter database clear unarchived logfile group 1;
alter database clear unarchived logfile group 1
*
ERROR at line 1:
ORA-01624: log 1 needed for crash recovery of instance xff (thread 1)
ORA-00312: online log 1 thread 1: ‘/u01/oradata/xienfei/redo01.log’
因为数据库恢复需要使用，不能被清空，尝试不完成恢复
SQL> recover database until cancel;
ORA-00279: change 1272687 generated at 08/24/2011 00:20:05 needed for thread 1
ORA-00289: suggestion : /u01/archive/1_27_756841839.arc
ORA-00280: change 1272687 for thread 1 is in sequence #27
Specify log: {=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 1272903 generated at 08/24/2011 00:25:17 needed for thread 1
ORA-00289: suggestion : /u01/archive/1_28_756841839.arc
ORA-00280: change 1272903 for thread 1 is in sequence #28
ORA-00278: log file ‘/u01/archive/1_27_756841839.arc’ no longer needed for this
recovery
ORA-00308: cannot open archived log ‘/u01/archive/1_28_756841839.arc’
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01194: file 1 needs more recovery to be consistent
ORA-01110: data file 1: ‘/u01/oradata/xienfei/system01.dbf’
已经提示数据不一致，尝试着打开数据库
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/oradata/xienfei/system01.dbf’
创建pfile文件，添加隐含参数，使之不进行检查点一致性校验
SQL> create pfile=’/tmp/pfile’ from spfile;
File created.
修改pfile ，添加以下参数
*._allow_resetlogs_corruption=TRUE
*._allow_error_simulation=TRUE
SQL> shutdown abort
ORACLE instance shut down.
使用pfile打开数据库
SQL> startup pfile=’/tmp/pfile’
ORACLE instance started.
Total System Global Area 167772160 bytes
Fixed Size 1260720 bytes
Variable Size 150995792 bytes
Database Buffers 8388608 bytes
Redo Buffers 7127040 bytes
Database mounted.
ORA-38760: This database instance failed to turn on flashback database
发现flashback导致数据库不能被正常打开，尝试关闭它
SQL> alter database flashback off;
Database altered.
尝试直接open数据库
SQL> alter database open;
alter database open
*
ERROR at line 1:
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
根据提示，使用resetlogs打开数据库
SQL> alter database open resetlogs;
Database altered.
查询日志状态
SQL> select a.group#,a.status,b.member from v$log a,v$logfile b where a.group#=b.group#;
GROUP# STATUS MEMBER
———- —————- ———————————————
3 UNUSED /u01/oradata/xienfei/redo03.log
2 UNUSED /u01/oradata/xienfei/redo02.log
1 CURRENT /u01/oradata/xienfei/redo01.log
因为group1错误，而当前日志组在group 1上，所以切换日志组
SQL> alter system switch logfile;
System altered.
SQL> select a.group#,a.status,b.member from v$log a,v$logfile b where a.group#=b.group#;
GROUP# STATUS MEMBER
———- —————- ———————————————
3 UNUSED /u01/oradata/xienfei/redo03.log
2 CURRENT /u01/oradata/xienfei/redo02.log
1 ACTIVE /u01/oradata/xienfei/redo01.log
SQL> alter system checkpoint;
System altered.
SQL> select a.group#,a.status,b.member from v$log a,v$logfile b where a.group#=b.group#;
GROUP# STATUS MEMBER
———- —————- ———————————————
3 UNUSED /u01/oradata/xienfei/redo03.log
2 CURRENT /u01/oradata/xienfei/redo02.log
1 INACTIVE /u01/oradata/xienfei/redo01.log
删除有问题的group 1日志组
SQL> alter database drop logfile group 1;
Database altered.
SQL> alter system switch logfile;
System altered.
添加日志组并检查是否正确
SQL> select a.group#,a.status,b.member from v$log a,v$logfile b where a.group#=b.group#;
GROUP# STATUS MEMBER
———- —————- ———————————————
3 CURRENT /u01/oradata/xienfei/redo03.log
2 ACTIVE /u01/oradata/xienfei/redo02.log
SQL> alter database add logfile group 1 ‘/u01/oradata/xienfei/redo01.log’ size 50m reuse;
Database altered.
SQL> alter system switch logfile;
System altered.
SQL> select a.group#,a.status,b.member from v$log a,v$logfile b where a.group#=b.group#;
GROUP# STATUS MEMBER
———- —————- ———————————————
3 ACTIVE /u01/oradata/xienfei/redo03.log
2 ACTIVE /u01/oradata/xienfei/redo02.log
1 CURRENT /u01/oradata/xienfei/redo01.log
注意：根据oracle官方建议，使用oracle隐含参数运行数据库可能存在很多不稳定因素，建议立即导出数据库数据，然后新建库，重新导入数据

#  使用alter database backup controlfile to trace;产生控制文件的trace file
-- Below are two sets of SQL statements, each of which creates a new
-- control file and uses it to open the database. The first set opens
-- the database with the NORESETLOGS option and should be used only if
-- the current versions of all online logs are available. The second
-- set opens the database with the RESETLOGS option and should be used
-- if online logs are unavailable.
-- The appropriate set of statements can be copied from the trace into
-- a script file, edited as necessary, and executed when there is a
-- need to re-create the control file.
#  需要重建控制文件的话， 如果online redo 是可用的, 使用NORESETLOGS 创建新控制文件打开数据库
#  如果online redo是不可用的, 那么需要使用RESETLOGS 创建新控制文件打开数据库,
#  联机日志被重置，数据有可能丢失
--
--     Set #1. NORESETLOGS case
--
-- The following commands will create a new control file and use it
-- to open the database.
-- Data used by Recovery Manager will be lost.
-- Additional logs may be required for media recovery of offline
-- Use this only if the current versions of all online logs are
-- available.
-- After mounting the created controlfile, the following SQL
-- statement will place the database in the appropriate
-- protection mode:
--  ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE
#   下面的命令用来创建一个新的控制文件来开启数据库。 用于RMAN的数据将会丢失。
#   对于offline datafiles 可能需要额外的归档日志用来做介质恢复，
#   当当前版本的所有online redo log都没有问题的情况下使用noresetlogs。
STARTUP NOMOUNT
CREATE CONTROLFILE REUSE DATABASE "XIENFEI" NORESETLOGS FORCE LOGGING ARCHIVELOG
    MAXLOGFILES 16
    MAXLOGMEMBERS 3
    MAXDATAFILES 100
    MAXINSTANCES 8
    MAXLOGHISTORY 2921
LOGFILE
  GROUP 1 '/u01/oradata/xienfei/redo01.log'  SIZE 5M,
  GROUP 2 '/u01/oradata/xienfei/redo02.log'  SIZE 5M,
  GROUP 3 '/u01/oradata/xienfei/redo03.log'  SIZE 5M
-- STANDBY LOGFILE
DATAFILE
  '/u01/oradata/xienfei/system01.dbf',
  '/u01/oradata/xienfei/undotbs01.dbf',
  '/u01/oradata/xienfei/sysaux01.dbf',
  '/u01/oradata/xienfei/users01.dbf',
  '/u01/oradata/xienfei/example01.dbf',
  '/u01/oradata/xienfei/xff01.dbf',
  '/u01/oradata/xienfei/cf01.dbf',
  '/u01/oradata/xienfei/cfxff01.dbf'
CHARACTER SET ZHS16GBK
;
-- Commands to re-create incarnation table
-- Below log names MUST be changed to existing filenames on
-- disk. Any one log file from each branch can be used to
-- re-create incarnation records.
-- ALTER DATABASE REGISTER LOGFILE '/u01/archive/1_1_756837539.arc';
#  有些时候可能需要先注册归档日志，再才能够恢复
-- Recovery is required if any of the datafiles are restored backups,
-- or if the last shutdown was not normal or immediate.
#  恢复数据库
RECOVER DATABASE
-- All logs need archiving and a log switch is needed.
#  归档所有日志
ALTER SYSTEM ARCHIVE LOG ALL;
-- Database can now be opened normally.
#  打开数据库
ALTER DATABASE OPEN;
-- Commands to add tempfiles to temporary tablespaces.
-- Online tempfiles have complete space information.
-- Other tempfiles may require adjustment.
#  添加临时表空间
ALTER TABLESPACE TEMP ADD TEMPFILE '/u01/oradata/xienfei/temp01.dbf'
     SIZE 32505856  REUSE AUTOEXTEND ON NEXT 655360  MAXSIZE 32767M;
-- End of tempfile additions.
##    下面的RESETLOGS 重建语句， online redo log 中的内容都会丢失，所有的备份将无效
##    仅仅在online log 损坏的情况下使用 resetlogs 创建控制文件开启数据库。
##    resetlog创建控制文件后的开启步骤与noresetlog有一些不一样，请注意下面步骤
--     Set #2. RESETLOGS case
--
-- The following commands will create a new control file and use it
-- to open the database.
-- Data used by Recovery Manager will be lost.
-- The contents of online logs will be lost and all backups will
-- be invalidated. Use this only if online logs are damaged.
-- After mounting the created controlfile, the following SQL
-- statement will place the database in the appropriate
-- protection mode:
--  ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE
STARTUP NOMOUNT
CREATE CONTROLFILE REUSE DATABASE "XIENFEI" RESETLOGS FORCE LOGGING ARCHIVELOG
    MAXLOGFILES 16
    MAXLOGMEMBERS 3
    MAXDATAFILES 100
    MAXINSTANCES 8
    MAXLOGHISTORY 2921
LOGFILE
  GROUP 1 '/u01/oradata/xienfei/redo01.log'  SIZE 5M,
  GROUP 2 '/u01/oradata/xienfei/redo02.log'  SIZE 5M,
  GROUP 3 '/u01/oradata/xienfei/redo03.log'  SIZE 5M
-- STANDBY LOGFILE
DATAFILE
  '/u01/oradata/xienfei/system01.dbf',
  '/u01/oradata/xienfei/undotbs01.dbf',
  '/u01/oradata/xienfei/sysaux01.dbf',
  '/u01/oradata/xienfei/users01.dbf',
  '/u01/oradata/xienfei/example01.dbf',
  '/u01/oradata/xienfei/xff01.dbf',
  '/u01/oradata/xienfei/cf01.dbf',
  '/u01/oradata/xienfei/cfxff01.dbf'
CHARACTER SET ZHS16GBK
;
-- Commands to re-create incarnation table
-- Below log names MUST be changed to existing filenames on
-- disk. Any one log file from each branch can be used to
-- re-create incarnation records.
#  注册归档日志
-- ALTER DATABASE REGISTER LOGFILE '/u01/archive/1_1_756837539.arc';
-- Recovery is required if any of the datafiles are restored backups,
-- or if the last shutdown was not normal or immediate.
#  使用历史控制文件恢复数据库（因为redo log是新建，所以对于redo 而言，控制文件是新建的）
RECOVER DATABASE USING BACKUP CONTROLFILE
-- Database can now be opened zeroing the online logs.
#  使用RESETLOGS方式打开数据库
ALTER DATABASE OPEN RESETLOGS;
-- Commands to add tempfiles to temporary tablespaces.
-- Online tempfiles have complete space information.
-- Other tempfiles may require adjustment.
#  添加临时表空间
ALTER TABLESPACE TEMP ADD TEMPFILE '/u01/oradata/xienfei/temp01.dbf'
     SIZE 32505856  REUSE AUTOEXTEND ON NEXT 655360  MAXSIZE 32767M;
-- End of tempfile additions.

一、oracle falshback drop
利用flashback drop oracle10g可以对DDL操作进行恢复,oracla提供类似回收站的recyclebin来收集被删除的对象，其实对象在删除的时候oracle把对象写到一个数据字典表中，当用户不需要该对象的时候，可以利用purge命令来从回收站进行清除
select object_name,droptime,dropscn,purge_object,ORIGINAL_NAME from recyclebin;
flashback table f_drop to before drop;
清空回收站：
1）清空一张表：purge table “BIN$N+i42FTvSSemvMrH6frCQg==$0″/table_name;
2）清空一个index：purge index index_name;
2）清空所有对象：PURGE recyclebin;
二、oracle falshback table
对于误drop的table此可以使用本操作，还原drop的table
select t_odu.*,ora_rowscn from a;–查询每条记录对应scn
select dbms_flashback.get_system_change_number from dual;–系统当前scn
alter table t_odu enable row movement;–table row movement
flashback table t_odu to scn 1831189;–基于scn恢复
flashback table t_odu to timestamp to_timestamp(‘2011-6-27 11:45:20′,’yyyy-mm-dd hh24:mi:ss’);–基于时间点
scn补充：
可以通过select ora_rowscn from table 得到每一条结果集当前的SCN，timestamp_to_scn()将scn转换到stmestamp；scn_to_timestamp()将timestamp转换到scn。
三、oracle falshback version query
racle10g falshback 能将所有做了提交的行进行记录，就类似于审计的功能，通过falshback可以查询什么时候执行了什么操作，非常方便，包括闪回版本的查询和审计等
select COUNT(*) from t_query as of scn 1831544;
SELECT COUNT(*) FROM t_query as of timestamp to_timestamp(‘2011-07-21 14:58:00′,’yyyy-mm-dd hh24:mi:ss’);
四、oracle falshback transaction query
回闪事务功能提供对过去某段时间内所完成的事务的查询和撤销
SELECT * FROM flashback_transaction_query a WHERE a.table_name=’T_QUERY’;
补充：
UNDO_SQL 就是当时对表T_QUERY的逆向操作语句

%c 备份片的拷贝数
%d 数据库名称
%D 位于该月中的第几天 (DD)
%M 位于该年中的第几月 (MM)
%F 一个基于DBID唯一的名称,这个格式的形式为c-IIIIIIIIII-YYYYMMDD-QQ,其中IIIIIIIIII为该数据库的DBID，YYYYMMDD为日期，QQ是一个1-256的序列
%n 数据库名称，向右填补到最大八个字符
%u 一个八个字符的名称代表备份集与创建时间
%p 该备份集中的备份片号，从1开始到创建的文件数
%U 一个唯一的文件名，代表%u_%p_%c
%s 备份集的号
%t 备份集时间戳
%T 年月日格式(YYYYMMDD)