[bbk4721] 第23集 第三章 Flashback Table 00

Objectives

After completing this lesson,you should be able to :

• Describe Flashback technology
• Perform Flashback Query
• Use Flashback Version Query
• Enable row movement on a table
• Perform Flashback Table operations
• Use Flashback Transaction Query
• Use Flashback Transaction

Preparing Your Database for Flashback

• Creating an undo tablespace
• Enabling Automatic Undo Management
• Specifying versus guaranteeing undo retention

Default database initialization parameters:

SQL> show parameter UNDO

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
undo_management                      string      AUTO
undo_retention                       integer     900
undo_tablespace                      string      UNDOTBS1

如何估算undo tablespace的容量？

首先将undo tablespace设置成，自动管理方式；然后DBA根据业务周期进行观察，由此判断出undo tablespace实际尺寸的大小.

参考动态性能试图v$undostat

SQL> select to_char(begin_time,'yyyy-mm-dd hh24:mi:ss') begin_time,to_char(end_time,'yyyy-mm-dd hh24:mi:ss') end

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-15 23:09:15 2013-05-15 23:19:15          2
2013-05-15 23:19:15 2013-05-15 23:29:15         48
2013-05-15 23:29:15 2013-05-15 23:39:15          0
2013-05-15 23:39:15 2013-05-15 23:49:15          0
2013-05-15 23:49:15 2013-05-15 23:59:15          1
2013-05-15 23:59:15 2013-05-16 00:09:15         57
2013-05-16 00:09:15 2013-05-16 00:19:15          2
2013-05-16 00:19:15 2013-05-16 00:29:15          0
2013-05-16 00:29:15 2013-05-16 00:39:15          1
2013-05-16 00:39:15 2013-05-16 00:49:15          2
2013-05-16 00:49:15 2013-05-16 00:59:15          0

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 00:59:15 2013-05-16 01:09:15         69
2013-05-16 01:09:15 2013-05-16 01:19:15          1
2013-05-16 01:19:15 2013-05-16 01:29:15          0
2013-05-16 01:29:15 2013-05-16 01:39:15          1
2013-05-16 01:39:15 2013-05-16 01:49:15          0
2013-05-16 01:49:15 2013-05-16 01:59:15          1
2013-05-16 01:59:15 2013-05-16 02:09:15         58
2013-05-16 02:09:15 2013-05-16 02:19:15          0
2013-05-16 02:19:15 2013-05-16 02:29:15          1
2013-05-16 02:29:15 2013-05-16 02:39:15          0
2013-05-16 02:39:15 2013-05-16 02:49:15          2

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 02:49:15 2013-05-16 02:59:15          1
2013-05-16 02:59:15 2013-05-16 03:09:15         82
2013-05-16 03:09:15 2013-05-16 03:19:15          1
2013-05-16 03:19:15 2013-05-16 03:29:15          1
2013-05-16 03:29:15 2013-05-16 03:39:15          0
2013-05-16 03:39:15 2013-05-16 03:49:15          0
2013-05-16 03:49:15 2013-05-16 03:59:15          0
2013-05-16 03:59:15 2013-05-16 04:09:15         72
2013-05-16 04:09:15 2013-05-16 04:19:15          1
2013-05-16 04:19:15 2013-05-16 04:29:15          1
2013-05-16 04:29:15 2013-05-16 04:39:15          1

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 04:39:15 2013-05-16 04:49:15          0
2013-05-16 04:49:15 2013-05-16 04:59:15          0
2013-05-16 04:59:15 2013-05-16 05:09:15         60
2013-05-16 05:09:15 2013-05-16 05:19:15          0
2013-05-16 05:19:15 2013-05-16 05:29:15          1
2013-05-16 05:29:15 2013-05-16 05:39:15          0
2013-05-16 05:39:15 2013-05-16 05:49:15          0
2013-05-16 05:49:15 2013-05-16 05:59:15          2
2013-05-16 05:59:15 2013-05-16 06:09:15         57
2013-05-16 06:09:15 2013-05-16 06:19:15          0
2013-05-16 06:19:15 2013-05-16 06:29:15          0

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 06:29:15 2013-05-16 06:39:15          1
2013-05-16 06:39:15 2013-05-16 06:49:15          0
2013-05-16 06:49:15 2013-05-16 06:59:15          1
2013-05-16 06:59:15 2013-05-16 07:09:15         68
2013-05-16 07:09:15 2013-05-16 07:19:15          0
2013-05-16 07:19:15 2013-05-16 07:29:15          1
2013-05-16 07:29:15 2013-05-16 07:39:15          1
2013-05-16 07:39:15 2013-05-16 07:49:15          0
2013-05-16 07:49:15 2013-05-16 07:59:15          1
2013-05-16 07:59:15 2013-05-16 08:09:15        155
2013-05-16 08:09:15 2013-05-16 08:19:15       1626

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 08:19:15 2013-05-16 08:29:15          2
2013-05-16 08:29:15 2013-05-16 08:39:15          0
2013-05-16 08:39:15 2013-05-16 08:49:15          0
2013-05-16 08:49:15 2013-05-16 08:59:15          0
2013-05-16 08:59:15 2013-05-16 09:09:15         68
2013-05-16 09:09:15 2013-05-16 09:19:15          0
2013-05-16 09:19:15 2013-05-16 09:29:15          1
2013-05-16 09:29:15 2013-05-16 09:39:15          0
2013-05-16 09:39:15 2013-05-16 09:49:15          1
2013-05-16 09:49:15 2013-05-16 09:59:15          1
2013-05-16 09:59:15 2013-05-16 10:09:15         82

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 10:09:15 2013-05-16 10:19:15          0
2013-05-16 10:19:15 2013-05-16 10:29:15          1
2013-05-16 10:29:15 2013-05-16 10:39:15          1
2013-05-16 10:39:15 2013-05-16 10:49:15          1
2013-05-16 10:49:15 2013-05-16 10:59:15          0
2013-05-16 10:59:15 2013-05-16 11:09:15         52
2013-05-16 11:09:15 2013-05-16 11:19:15          5
2013-05-16 11:19:15 2013-05-16 11:29:15          2
2013-05-16 11:29:15 2013-05-16 11:39:15          3
2013-05-16 11:39:15 2013-05-16 11:49:15          1
2013-05-16 11:49:15 2013-05-16 11:59:15          0

BEGIN_TIME          END_TIME              UNDOBLKS
------------------- ------------------- ----------
2013-05-16 11:59:15 2013-05-16 12:04:28         57

78 rows selected.