升級失敗后，數據庫降級方案(flashback database)

環境：Oracle 11.2.0.1 rac on redhat 5.8

Flashback database

準備工作

查看是否flashback database功能

sys@RACDB>

select log_mode,open_mode,flashback_on from

v$database;

LOG_MODE

OPEN_MODE??????????? FLASHBACK_ON

------------ -------------------- ------------------

ARCHIVELOG?? READ

WRITE?????????? NO

--

未開啟flashback

database 功能

查看是否設置了閃回目錄、閃回目錄空間大小

sys@RACDB> show parameter db_recovery

NAME

TYPE??????? VALUE

------------------------------------ -----------

------------------------------

db_recovery_file_dest??????????????? string

db_recovery_file_dest_size?????????? big integer 0

--

顯然我們沒有設置，下面為設置后

alter system set db_recovery_file_dest='+DATA' scope=spfile

sid='*';

--

重啟后生效

alter system set db_recovery_file_dest_size=4g;

sys@RACDB> show parameter db_recovery

NAME???????????????????????????????? TYPE??????? VALUE

------------------------------------ ----------- ------------------------------

db_recovery_file_dest??????????????? string????? +DATA

db_recovery_file_dest_size?????????? big integer 4G

設置閃回保留期

sys@RACDB> show parameter db_flashback

NAME???????????????????????????????? TYPE??????? VALUE

------------------------------------ -----------

------------------------------

db_flashback_retention_target??????? integer???? 1440

--

缺省單位為分鐘

Flashback database

開啟工作

開啟flashback database功能

sys@RACDB> alter database flashback on;

Database altered.

sys@RACDB> select status from gv$instance;

STATUS

------------

OPEN

OPEN

sys@RACDB> select log_mode,open_mode,flashback_on from

v$database;

LOG_MODE

OPEN_MODE??????????? FLASHBACK_ON

------------ -------------------- ------------------

ARCHIVELOG?? READ

WRITE?????????? YES

–-開啟了flashback

database功能

oracle 10.2.0.1

開啟flashback database

需要在mount，且只有一個實例的情況下，否則會報錯

ORA-38759: Database must be mounted by only one instance and

not open.

oracle 11.2.0.1

開啟flashback database在open狀態下，且多個實例共存，沒有任何問題

查看允許閃回的最早時間點

select oldest_flashback_scn

old_flhbck_scn,oldest_flashback_time old_flhbck_tim,

retention_target

rete_trgt,flashback_size/1024/1024 flhbck_siz,

estimated_flashback_size/1024/1024

est_flhbck_size

from v$flashback_database_log;

OLD_FLHBCK_SCN OLD_FLHBCK_TIM?????? RETE_TRGT FLHBCK_SIZ EST_FLHBCK_SIZE

-------------- ------------------- ---------- ----------

---------------

1602195 2013-08-08

16:48:34?????? 1440???? 15.625?????????????? 0

Flashback database

使用范例

1

、創建一個restore point

升級失敗后，降級時使用flashback database to restore point upgrade_dou;。

sys@RACDB> create restore point upgrade_dou guarantee

flashback database;

Restore point created.

sys@RACDB> select oldest_flashback_scn

old_flhbck_scn,oldest_flashback_time old_flhbck_tim,

2? retention_target

rete_trgt,flashback_size/1024/1024 flhbck_siz,

3? estimated_flashback_size/1024/1024

est_flhbck_size

4? from v$flashback_database_log;

OLD_FLHBCK_SCN OLD_FLHBCK_TIM?????? RETE_TRGT FLHBCK_SIZ EST_FLHBCK_SIZE

-------------- ------------------- ---------- ----------

---------------

1602195 2013-08-08

16:48:34?????? 1440???? 15.625??????? 143.8125

2

、flashback database使用restore

point

降級時

數據庫必須是mount狀態

sys@RACDB>

flashback database to restore point upgrade_dou;

flashback database to restore point upgrade_dou

*

ERROR at line 1:

ORA-38757: Database must be mounted and not open to FLASHBACK.

Flashback database

必須resetlogs open數據庫

sys@RACDB> alter database open;

alter database open

*

ERROR at line 1:

ORA-01589: must use RESETLOGS or NORESETLOGS option for

database open

RAC

環境中alter database open resetlogs;時有且只有一個實例執行resetlogs

idle> select status from gv$instance;

STATUS

------------

MOUNTED

MOUNTED

idle> alter database open resetlogs;

alter database open resetlogs

*

ERROR at line 1:

ORA-38777: database must not be started in any other instance

關閉一個節點

idle> select status from gv$instance;

STATUS

------------

MOUNTED

idle> alter database open resetlogs;

Database altered.

檢查RAC節點恢復情況

另一個節點也open

idle> select status from gv$instance;

STATUS

------------

OPEN

OPEN

idle>

select current_scn from gv$database;

CURRENT_SCN

-----------

1628773

1628774

附表

查看允許閃回的最早時間點

select

oldest_flashback_scn old_flhbck_scn,oldest_flashback_time old_flhbck_tim,

retention_target rete_trgt,flashback_size/1024/1024

flhbck_siz,

estimated_flashback_size/1024/1024

est_flhbck_size

from

v$flashback_database_log;

查看sga中分配的閃回空間大小

select

*

from

v$sgastat

where

name

like

'flashback%';

POOL???????? NAME??????????????????????????? BYTES

------------

-------------------------- ----------

shared pool? flashback generation buff???? 3981204

shared pool? flashback_marker_cache_si??????? 9196

查看閃回區的使用情況

select

name,space_limit/1024/1024 sp_limt,space_used/1024/1024 sp_usd,space_reclaimable/1024/1024

sp_recl,number_of_files num_fils

from

v$recovery_file_dest;

NAME

----------------------------------------------------------------------------------------------------

SP_LIMT???? SP_USD

SP_RECL?? NUM_FILS

---------- ---------- ---------- ----------

+DATA

4096???????? 36????????? 0????????? 3

使用flashback database閃回數據庫

步驟(前提歸檔日志可用)

關閉數據庫

啟動數據庫到mount狀態(exclusive模式)

閃回至某個時間點，SCN或log sequence number

使用resetlogs打開數據庫

1.

使用sqlplus實現閃回

可以接受一個時間標記或一個系統改變號實參

sqlplus

幾種常用的閃回數據庫方法

FLASHBACK [STANDBY]

DATABASE []

TO [BEFORE] SCN

--

基于SCN閃回

FLASHBACK [STANDBY]

DATABASE []

TO [BEFORE] TIMESTMP --

基于時間戳閃回

FLASHBACK [STANDBY]

DATABASE []

TO [BEFORE] RESTORE POINT --

基于時點閃回

如下面的示例：

SQL>

flashback

database

to

timestamp('2010-10-24

13:04:30','yyyy-mm-dd hh24:mi:ss');

SQL>

flashback

database

to

scn 918987;

SQL>

flashback

database

ro

restore

point b1_load;

2.

使用RMAN進行flashback

database

使用RMAN進行閃回數據庫的幾種常用辦法

RMAN>

flashback

database

to

scn=918987;

RMAN>

flashback

database

to

sequence=85

thread=1;

參考文獻:

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