Databases Reference
In-Depth Information
USERID=sh/sh
DUMPFILE=shSales
DIRECTORY=default_dp_dest
JOB_NAME=shSalesCompleteDump
TABLES=SALES
LOGFILE=default_log_dest:shSales
The parameter file is a plain text format file. You may use your own naming
conventions. Oracle regularly uses .par for the parameter files, in this case it used
.dpp
to denote a Data Pump parameter file. The file name can be dynamically defined using
environment variables, but this file name formatting is beyond the scope of Oracle and
it exclusively depends on the OS variable management.
JOBNAME
(
C
) is the option to specify a non-default job name, otherwise oracle will
use a name for it. It is good practice to have the job name explicitly defined so the
user can
ATTACH
to it at a later time, and related objects such as the
Master
table
(
B
) can be more easily identified.
Retrieve original data
In some circumstances, it may be useful to export the image of a table the way it
existed before a change was committed. If the database is properly configured,
the database flashback query facility—also integrated with
dpexp
—may be used.
It is useful for obtaining a consistent exported table image.
In this example a copy of the original
HR.EMPLOYEES
table is made
(
HR.BAK_EMPLOYEES
), and all the tasks will update the
BAK_EMPLOYEES
table
contents. A
Restore Point
is created so that you can easily find out the exact time
stamp when this change took place:
SQL> CREATE RESTORE POINT ORIGINAL_EMPLOYEES;
Restore point created.
SQL> SELECT SCN, NAME FROM V$RESTORE_POINT;
SCN NAME
---------- --------------------------------
621254 ORIGINAL_EMPLOYEES
SQL> SELECT SUM(SALARY) FROM EMPLOYEES;
SUM(SALARY)
-----------
691400
This is the way data was, at the referred SCN. This number will be used later,
to perform the
expdp
operation and retrieve data as it was, at this point in time.
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