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== DBMS_FLASHBACK.ENABLE_AT_SYSTEM_CHANGE_NUMBER() procedure enables you to perform a flashback to an SCN.==



<source lang="sql">
SQL>
SQL> VARIABLE current_scn NUMBER
SQL> EXECUTE :current_scn := DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER();
PL/SQL procedure successfully completed.
SQL> PRINT current_scn
CURRENT_SCN
-----------
5547739
SQL>
SQL> EXECUTE DBMS_FLASHBACK.ENABLE_AT_SYSTEM_CHANGE_NUMBER(:current_scn);
BEGIN DBMS_FLASHBACK.ENABLE_AT_SYSTEM_CHANGE_NUMBER(:current_scn); END;

SQL>
--</source>

== Granting the Privilege for Using Flashbacks==

The following example connects as the sys user and grants the EXECUTE privilege on DBMS_FLASHBACK to the store user:



<source lang="sql">
CONNECT sys/change_on_install AS sysdba
GRANT EXECUTE ON SYS.DBMS_FLASHBACK TO store;</source>

== Query Flashbacks==

If you mistakenly commit changes and you want to view rows as they originally were, you can use a query flashback.
You can then use the results of a query flashback to manually change rows back to their original values if you need to.
In addition, flashbacks can be based on a datetime or system change number (SCN).
The database uses SCNs to track changes made to data, and you can use them to flash back to a particular SCN in the database.
35. 6. Flashbacks
35. 6. 1.
Query Flashbacks
35. 6. 2.
<A href="/Tutorial/Oracle/0680__Transaction/GrantingthePrivilegeforUsingFlashbacks.htm">Granting the Privilege for Using Flashbacks</a>
35. 6. 3.
<A href="/Tutorial/Oracle/0680__Transaction/TimeQueryFlashbacks.htm">Time Query Flashbacks</a>
35. 6. 4.
<A href="/Tutorial/Oracle/0680__Transaction/TodisableaflashbackyouexecuteDBMSFLASHBACKDISABLE.htm">To disable a flashback, you execute DBMS_FLASHBACK.DISABLE()</a>
35. 6. 5.
<A href="/Tutorial/Oracle/0680__Transaction/SystemChangeNumberQueryFlashbacks.htm">System Change Number Query Flashbacks</a>
35. 6. 6.
<A href="/Tutorial/Oracle/0680__Transaction/DBMSFLASHBACKENABLEATSYSTEMCHANGENUMBERprocedureenablesyoutoperformaflashbacktoanSCN.htm">DBMS_FLASHBACK.ENABLE_AT_SYSTEM_CHANGE_NUMBER() procedure enables you to perform a flashback to an SCN.</a>

== System Change Number Query Flashbacks==

Flashbacks based on system change numbers (SCNs) can be more precise than those based on a time, because the database uses SCNs to track changes.



<source lang="sql">
SQL> VARIABLE current_scn NUMBER
SQL> EXECUTE :current_scn := DBMS_FLASHBACK.GET_SYSTEM_CHANGE_NUMBER();
PL/SQL procedure successfully completed.
SQL> PRINT current_scn
CURRENT_SCN
-----------
5547739
SQL></source>

== Time Query Flashbacks==



<source lang="sql">
SQL>
SQL> EXECUTE DBMS_FLASHBACK.ENABLE_AT_TIME(SYSDATE - 10 / 1440);
BEGIN DBMS_FLASHBACK.ENABLE_AT_TIME(SYSDATE - 10 / 1440); END;</source>

== To disable a flashback, you execute DBMS_FLASHBACK.DISABLE()==



<source lang="sql">
SQL>
SQL> EXECUTE DBMS_FLASHBACK.DISABLE();
PL/SQL procedure successfully completed.</source>

You must disable a flashback before you can enable it again.

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