跨数据文件删除flashback database

Oracle flashback database的使用有一些限制，其中最主要的是flashback database不支持跨数据文件删除闪回和不支持跨数据文件shrink闪回。对于已经删除的数据文件只能采用恢复机制进行恢复，具体操作方法见以下测试。

1. 测试环境准备

1.1 开启flashback

检查flashback是否开启，如未开启，先开启flashback.
SQL> select flashback_on from v$database;

FLASHBACK_ON
------------------
YES

检查当前scn
SQL> select current_scn from v$database;

CURRENT_SCN
-----------
    1295139

检查当前归档日志
SQL> select max(sequence#) from v$archived_log;

MAX(SEQUENCE#)
--------------
           56

1.2 创建表空间、用户、表，插入数据

创建测试表空间
SQL> create tablespace testtbs datafile '+DATA/beicenp/datafile/testtbs.dbf' size 10m autoextend on;

Tablespace created.

SQL> alter system archive log current;

System altered.

SQL> select max(sequence#) from v$archived_log;

MAX(SEQUENCE#)
--------------
           57

创建测试用户
SQL> create user test identified by test default tablespace testtbs;

User created.

SQL> grant connect,resource to test;

Grant succeeded.

SQL> create table test.testtb (id number);

Table created.

SQL> insert into test.testtb values (1);

1 row created.

SQL> commit;

Commit complete.

SQL> alter system archive log current;

System altered.

SQL> select current_scn from v$database;

CURRENT_SCN
-----------
    1295236

1.3 执行数据库备份

执行以下脚本备份数据库：
run {
 allocate channel ch00 type disk;
 backup as compressed backupset format '/app/oracle/bk_%s_%p_%t' database;
 sql 'alter system archive log current';
 backup as compressed backupset format '/app/oracle/arch_%s_%p_%t' archivelog all delete input;
 backup format '/app/oracle/cntl_%s_%p_%t' current controlfile;
 release channel ch00;
}

1.4 备份后模拟一些数据库操作

模拟一些数据库操作：
SQL> insert into test.testtb values (2);

1 row created.

SQL> commit;

Commit complete.

SQL> alter system archive log current;

System altered.

SQL> select current_scn from v$database;

CURRENT_SCN
-----------
    1295364

SQL> insert into test.testtb values (3);

1 row created.

SQL> commit;

Commit complete.

SQL> alter system archive log current;

System altered.

SQL> select current_scn from v$database;

CURRENT_SCN
-----------
    1296106

flashback database时闪回到此scn

1.5 删除测试表空间

模拟表空间删除：
SQL> drop tablespace testtbs including contents and datafiles;

Tablespace dropped.

SQL> select * from test.testtb;
select * from test.testtb
                   *
ERROR at line 1:
ORA-00942: table or view does not exist

SQL> alter system archive log current;

System altered.

2. 闪回测试

2.1 执行闪回

关闭数据库，并启动到mount状态：
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup mount;
ORACLE instance started.

Total System Global Area 1052233728 bytes
Fixed Size                  2217704 bytes
Variable Size             805308696 bytes
Database Buffers          239075328 bytes
Redo Buffers                5632000 bytes
Database mounted.

检查数据库是否能够闪回的所需要的SCN：
SQL> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';

Session altered.

SQL> set lines 120
SQL> select OLDEST_FLASHBACK_SCN,OLDEST_FLASHBACK_TIME,RETENTION_TARGET,FLASHBACK_SIZE/1024/1024/1024 as size_G,ESTIMATED_FLASHBACK_SIZE/1024/1024/1024 as estimate_size_G from v$flashback_database_log;

OLDEST_FLASHBACK_SCN OLDEST_FLASHBACK_TI RETENTION_TARGET     SIZE_G ESTIMATE_SIZE_G
-------------------- ------------------- ---------------- ---------- ---------------
             1295593 2014-01-03 10:00:15             1440 .007629395               0

执行闪回操作：
SQL> flashback database to scn 1296106;
flashback database to scn 1296106
*
ERROR at line 1:
ORA-38795: warning: FLASHBACK succeeded but OPEN RESETLOGS would get error below
ORA-01245: offline file 5 will be lost if RESETLOGS is done
ORA-01111: name for data file 5 is unknown - rename to correct file
ORA-01110: data file 5: '/app/oracle/product/10.2/dbs/UNNAMED00005'
闪回时数据库会报错，因为flashback不支持跨数据文件删除操作。

此时alert日志中的闪回信息如下：

Fri Jan  3 10:13:22 2014
flashback database to scn 1296106
Fri Jan  3 10:13:23 2014
Flashback Restore Start
Flashback: created tablespace #6: 'TESTTBS' in the controlfile.
Flashback: created OFFLINE file 'UNNAMED00005' for tablespace #6 in the controlfile.
Filename was:
'+DATA/beicenp/datafile/testtbs.dbf' when dropped.
File will have to be restored from a backup and recovered.
Flashback Restore Complete
Flashback Media Recovery Start
 parallel recovery started with 2 processes
Fri Jan  3 10:13:24 2014
Recovery of Online Redo Log: Thread 1 Group 2 Seq 62 Reading mem 0
  Mem# 0 errs 0: +DATA/beicenp/onlinelog/group_2.258.798647877
  Mem# 1 errs 0: +FLASH/beicenp/onlinelog/group_2.258.798647877
Fri Jan  3 10:13:26 2014
Recovery of Online Redo Log: Thread 1 Group 3 Seq 63 Reading mem 0
  Mem# 0 errs 0: +DATA/beicenp/onlinelog/group_3.259.798647879
  Mem# 1 errs 0: +FLASH/beicenp/onlinelog/group_3.259.798647881
Fri Jan  3 10:13:26 2014
Incomplete Recovery applied until change 1296111
Flashback Media Recovery Complete
ORA-38795 signalled during: flashback database to scn 1296106...

日志中明确说明被删除的数据文件需要从备份中恢复。

2.2 恢复数据文件

被删除的数据文件需要使用备份的控制文件才能恢复，不能使用当前控制文件进行恢复。

关闭数据库并启动到nomount状态：
SQL> shutdown immediate;
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
SQL> startup nomount
ORACLE instance started.

Total System Global Area  935329792 bytes
Fixed Size                  2025168 bytes
Variable Size             310380848 bytes
Database Buffers          616562688 bytes
Redo Buffers                6361088 bytes

执行以下脚本恢复控制文件、数据文件和归档日志：
run {
 allocate channel ch00 type disk;
 restore controlfile from '/app/oracle/cntl_8_1_835869096';
 sql 'alter database mount';
 restore datafile 5;
 restore archivelog from sequence 58;
 release channel ch00;
}

然后执行database recover：
SQL> recover database using backup controlfile until change 1296106;
ORA-00279: change 1295287 generated at 01/03/2014 09:50:41 needed for thread 1
ORA-00289: suggestion : +ARCH
ORA-00280: change 1295287 for thread 1 is in sequence #59

Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
auto
ORA-00279: change 1295313 generated at 01/03/2014 09:51:23 needed for thread 1
ORA-00289: suggestion : +ARCH
ORA-00280: change 1295313 for thread 1 is in sequence #60
ORA-00278: log file
'+ARCH/beicenp/archivelog/2014_01_03/thread_1_seq_59.286.835871009' no longer
needed for this recovery

ORA-00279: change 1295318 generated at 01/03/2014 09:51:23 needed for thread 1
ORA-00289: suggestion : +ARCH
ORA-00280: change 1295318 for thread 1 is in sequence #61
ORA-00278: log file
'+ARCH/beicenp/archivelog/2014_01_03/thread_1_seq_60.289.835871011' no longer
needed for this recovery

ORA-00279: change 1295363 generated at 01/03/2014 09:52:04 needed for thread 1
ORA-00289: suggestion : +ARCH
ORA-00280: change 1295363 for thread 1 is in sequence #62
ORA-00278: log file
'+ARCH/beicenp/archivelog/2014_01_03/thread_1_seq_61.283.835869125' no longer
needed for this recovery

ORA-00279: change 1296104 generated at 01/03/2014 10:00:45 needed for thread 1
ORA-00289: suggestion : +ARCH
ORA-00280: change 1296104 for thread 1 is in sequence #63
ORA-00278: log file
'+ARCH/beicenp/archivelog/2014_01_03/thread_1_seq_62.284.835869645' no longer
needed for this recovery

Log applied.
Media recovery complete.

recover完成后，以resetlogs方式打开：
SQL> alter database open resetlogs;

Database altered.

打开后检查测试数据：
SQL> select * from test.testtb;

        ID
----------
         3
         1
         2

以下是尝试用当前控制文件恢复数据文件

执行数据库闪回：
SQL> flashback database to scn 1296106;
flashback database to scn 1296106
*
ERROR at line 1:
ORA-38795: warning: FLASHBACK succeeded but OPEN RESETLOGS would get error
below
ORA-01245: offline file 5 will be lost if RESETLOGS is done
ORA-01111: name for data file 5 is unknown - rename to correct file
ORA-01110: data file 5: '/app/oracle/product/10.2/dbs/UNNAMED00005'
因数据文件已经被删除，闪回报错。

创建数据文件：
SQL> alter database create datafile '/app/oracle/product/10.2/dbs/UNNAMED00005' as '+DATA/beicenp/datafile/testtbs.dbf';

Database altered.

执行RMAN脚本，恢复数据文件及归档日志：
run {
 allocate channel ch00 type disk;
 restore datafile 5;
 restore archivelog from sequence 58;
 release channel ch00;
}

再次执行闪回：
SQL> flashback database to scn 1296106;
flashback database to scn 1296106
*
ERROR at line 1:
ORA-38795: warning: FLASHBACK succeeded but OPEN RESETLOGS would get error
below
ORA-01245: offline file 5 will be lost if RESETLOGS is done
ORA-01110: data file 5: '+DATA/beicenp/datafile/testtbs.dbf'
闪回依然报错。网上有些测试说在创建文件后再执行闪回，就可以恢复被删除的数据文件。其前提条件是需要有文件创建以来的所有归档日志。很多时候这个条件并不是很容易满足。

测试使用当前控制文件恢复：
SQL> recover database until change 1296106;
ORA-01547: warning: RECOVER succeeded but OPEN RESETLOGS would get error below
ORA-01245: offline file 5 will be lost if RESETLOGS is done
ORA-01110: data file 5: '+DATA/beicenp/datafile/testtbs.dbf'
恢复仍然报错。这说明flashback后是不能使用当前控制文件恢复被删除的数据文件的，必须使用备份的控制文件。如果此时将控制文件替换为备份控制文件，然后再执行恢复，恢复仍然能够成功。