Flashback query enables you to see how the table looked in the past. Or the table changes between two time periods.
VERSIONS BETWEEN TIMESTAMP SYSTIMESTAMP - INTERVAL '20:00' MINUTE TO SECOND
AND SYSTIMESTAMP
Finds all the changes to the table in the past 20 minutes. The versions* columns are pseudocolumns showing:
VERSIONS_STARTTIME - when this change happened
VERSIONS_XID - the transaction that made the change
VERSIONS_OPERATION - If this was an I(nsert), U(pdate) or D(elete)
You can read more about this at:
https://docs.oracle.com/cd/E11882_01/appdev.112/e41502/adfns_flashback.htm#ADFNS1008 https://oracle-base.com/articles/10g/flashback-10g#flashback_query