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redo的构成

原创 Linux操作系统 作者:lawzjf 时间:2005-07-14 00:00:00 0 删除 编辑

To illustrate the creation of change vectors and redo records, consider the following transaction:

Ø

SQL> update emp set empno = 22 where empno = 11
Ø
When this update statement is executed , the sequence of operation is as follows:
1.Change vectors of the redo record are generated
2.The redo record is saved in a redo log buffer
3.The change vectors are applied to the data blocks
ØThe redo records stated in step 1 contains three change vectors
- Change to the transaction table of rollback segment
- Change to the rollback segment datablock
- Change to the data segment block belonging to the EMP table

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