Oracle备份恢复之Trial Recovery

 

Oracle备份恢复之 Trial Recovery

一 什么是 Trial Recovery

官方解释：A trial recovery applies redo in a way similar to normal media recovery, but it never writes its changes to disk and it always rolls back its changes. Trial recovery occurs only in memory.

trial recovery基本上类似于正常的介质恢复，应用redo的过程仅仅发生在内存中，不会把数据的改变写到磁盘。说白了就是测试介质恢复过程

 

二 Trial Recovery如何工作

1 默认，如果恢复由于数据块损坏而卡住或者遇到类似问题，会标记相关块以求继续恢复，同时写错误信息到alert文件。

2 当遭遇如下问题时，Trial Recovery过程会结束

 

● 超出内存buffer限制

● 遭遇一个不可恢复性错误，即使通过标记坏块也不能解决，比如文件丢失

● 用户取消或者终止恢复会话

● 所有必须的redo已经被应用，即不需要恢复。

当 trial recovery 结束，一切恢复原样，只是错误消息会记录在alter 文件中。运行测试时，注意排除由于内存原因造成测试过程结束的影响。

 

三 Trial Recovery 的语句

recover ……..test

例如：

recover database test

recover database using backup controlfile until cancel test

recover tablespace users test

recover database until cancel test

 

注意： 默认trial recovery会在内存中标记（无限制）的坏块，使恢复过程能够继续进行。我们可以指定 allow n corruption 语句 在 recover…..test 后面，以限制可以标记的坏块数。

 

四 测试过程

正常情况：

RMAN> recover database test;

 

Starting recover at 05-DEC-12

using channel ORA_DISK_1

starting media recovery

archive log thread 1 sequence 1 is already on disk as file /oracle/archive/1_1_801229657.dbf

archive log thread 1 sequence 2 is already on disk as file /oracle/archive/1_2_801229657.dbf

archive log thread 1 sequence 3 is already on disk as file /oracle/archive/1_3_801229657.dbf

archive log thread 1 sequence 4 is already on disk as file /oracle/archive/1_4_801229657.dbf

archive log thread 1 sequence 5 is already on disk as file /oracle/archive/1_5_801229657.dbf

archive log thread 1 sequence 6 is already on disk as file /oracle/archive/1_6_801229657.dbf

archive log thread 1 sequence 7 is already on disk as file /oracle/archive/1_7_801229657.dbf

archive log thread 1 sequence 8 is already on disk as file /oracle/archive/1_8_801229657.dbf

archive log thread 1 sequence 9 is already on disk as file /oracle/archive/1_9_801229657.dbf

archive log thread 1 sequence 10 is already on disk as file /oracle/archive/1_10_801229657.dbf

archive log thread 1 sequence 11 is already on disk as file /oracle/archive/1_11_801229657.dbf

archive log thread 1 sequence 12 is already on disk as file /oracle/archive/1_12_801229657.dbf

archive log thread 1 sequence 13 is already on disk as file /oracle/archive/1_13_801229657.dbf

archive log thread 1 sequence 14 is already on disk as file /oracle/archive/1_14_801229657.dbf

archive log filename=/oracle/archive/1_1_801229657.dbf thread=1 sequence=1

archive log filename=/oracle/archive/1_2_801229657.dbf thread=1 sequence=2

archive log filename=/oracle/archive/1_3_801229657.dbf thread=1 sequence=3

archive log filename=/oracle/archive/1_4_801229657.dbf thread=1 sequence=4

archive log filename=/oracle/archive/1_5_801229657.dbf thread=1 sequence=5

archive log filename=/oracle/archive/1_6_801229657.dbf thread=1 sequence=6

archive log filename=/oracle/archive/1_7_801229657.dbf thread=1 sequence=7

archive log filename=/oracle/archive/1_8_801229657.dbf thread=1 sequence=8

archive log filename=/oracle/archive/1_9_801229657.dbf thread=1 sequence=9

RMAN-11006: WARNING: test recovery results:

ORA-10574: Test recovery did not corrupt any data block

ORA-10573: Test recovery tested redo from change 2779426987 to 2779427975

ORA-10572: Test recovery canceled due to errors

ORA-10581: Can not modify redo log header during test recovery

media recovery complete, elapsed time: 00:00:00

Finished recover at 05-DEC-12

 

移除其中一个归档后则情况如下：

 

RMAN> recover database test;     

 

Starting recover at 05-DEC-12

using channel ORA_DISK_1

 

starting media recovery

 

archive log thread 1 sequence 1 is already on disk as file /oracle/archive/1_1_801229657.dbf

archive log thread 1 sequence 2 is already on disk as file /oracle/archive/1_2_801229657.dbf

archive log thread 1 sequence 3 is already on disk as file /oracle/archive/1_3_801229657.dbf

archive log thread 1 sequence 4 is already on disk as file /oracle/archive/1_4_801229657.dbf

archive log thread 1 sequence 5 is already on disk as file /oracle/archive/1_5_801229657.dbf

archive log thread 1 sequence 6 is already on disk as file /oracle/archive/1_6_801229657.dbf

archive log thread 1 sequence 7 is already on disk as file /oracle/archive/1_7_801229657.dbf

archive log thread 1 sequence 8 is already on disk as file /oracle/archive/1_8_801229657.dbf

archive log thread 1 sequence 9 is already on disk as file /oracle/archive/1_9_801229657.dbf

archive log thread 1 sequence 11 is already on disk as file /oracle/archive/1_11_801229657.dbf

archive log thread 1 sequence 12 is already on disk as file /oracle/archive/1_12_801229657.dbf

archive log thread 1 sequence 13 is already on disk as file /oracle/archive/1_13_801229657.dbf

archive log thread 1 sequence 14 is already on disk as file /oracle/archive/1_14_801229657.dbf

RMAN-11006: WARNING: test recovery results:

ORA-10574: Test recovery did not corrupt any data block

ORA-10573: Test recovery tested redo from change 2779426987 to 2779426987

ORA-10571: Test recovery canceled

 

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-03002: failure of recover command at 12/05/2012 20:59:16

RMAN-06053: unable to perform media recovery because of missing log

RMAN-06025: no backup of log thread 1 seq 10 lowscn 2779427837 found to restore

上面错误提示可清晰看到提示日志文件丢失提示

不过感觉这命令还不如下面命令好用

 

RMAN> restore validate archivelog sequence between 1 and 14;

 

Starting restore at 05-DEC-12

using channel ORA_DISK_1

 

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-03002: failure of restore command at 12/05/2012 21:08:18

RMAN-06026: some targets not found - aborting restore

RMAN-06025: no backup of log thread 1 seq 10 lowscn 2779427837 found to restore