Relationship between scn and timestamp

To query past data at a precise time, use an SCN. If you use a time stamp, 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 time stamps at a granularity of 3 seconds.

For example, suppose that the SCN values 1000 and 1005 are mapped to the time stamps 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.

Therefore, 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 immediately before the DDL operation, causing error ORA-01466.


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