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Richard Niemiec

"Oracle Database 10g Performance Tuning Tips & Techniques"


Note that in this example, using the command line would take less time and is probably more
straightforward; however, if you have unknown dependencies or if the command-line syntax is
unfamiliar to you, then EM Database Control is a better option.
Flashback Version Query
Flashback Version Query, another Flashback feature that relies on undo data, provides a finer
level of detail than an as of query: Whereas the Flashback methods we??™ve presented up to now
bring back rows of a table or an entire table for a particular point in time, Flashback Version
Query will return the entire history of a given row between two SCNs or timestamps.
For the examples in this and the next section, the user HR makes a number of changes to the
HR.EMPLOYEES and HR.DEPARTMENTS tables:
SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
4011365
SQL> update hr.employees set salary = salary*1.2 where employee_id=195;
1 row updated.
SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
4011381
SQL> delete from hr.employees where employee_id = 196;
1 row deleted.
SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
4011409
SQL> insert into hr.departments values (660,'Security', 100, 1700);
1 row created.
SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
4011433
SQL> update hr.


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