EMERGENCY: Need to flashback table, how to find SCN for a time before update happened?

Question

Hi all,
I've got a new database 11G, I've not used flashback before, but my retention time is a day...I have a time that the developer did a massive update to a table to corrupt it.
How do I find the SCN for that time so I can attempt to flashback that table?
Thank you,
cayenne

Answer 1

Thank you..I also found this works:
SQL> select timestamp_to_scn(to_timestamp('20140103152000','YYYYMMDDHH24MISS')) scn from dual;
       SCN
  98344246
Well that might NOT work all of the time. But that is just what Oracle does when you give it a timestamp to flashback to: it converts the timestamp to an SCN and then restores data based on that SCN.
See Flashback Table in the SQL Language doc
http://docs.oracle.com/cd/B28359_01/server.111/b28286/statements_9012.htm
TO TIMESTAMP Clause
Specify a timestamp value corresponding to the point in time to which you want to return the table. The expr must evaluate to a valid timestamp in the past. The table will be flashed back to a time within approximately 3 seconds of the specified timestamp.
That 'approximately 3 seconds' accuracy is due to that conversion to SCN - Oracle uses its internal table.
SCN is accurate if you know it but you usually don't.
Read, and heed, these warnings in the advanced app dev guide
http://docs.oracle.com/cd/B28359_01/appdev.111/b28424/adfns_flashback.htm
Guidelines for Oracle Flashback Query
  If a possible 3-second error (maximum) is important to Oracle Flashback Query in your application, use an SCN instead of a timestamp. See General Guidelines for Oracle Flashback Technology.
General Guidelines for Oracle Flashback Table
  To query past data at a precise time, use an SCN. If you use a timestamp, the actual time queried might be up to 3 seconds earlier than the time you specify. Oracle Database uses SCNs internally and maps them to timestamps at a granularity of 3 seconds.
     For example, suppose that the SCN values 1000 and 1005 are mapped to the timestamps 8:41 AM and 8:46 AM, respectively. A query for a time between      8:41:00 and 8:45:59 AM is mapped to SCN 1000; an Oracle Flashback Query for 8:46 AM is mapped to SCN 1005.
     Due to this time-to-SCN mapping, if you specify a time that is slightly after a DDL operation (such as a table creation) Oracle Database might use an SCN      that is just before the DDL operation, causing error ORA-1466.