- For general users if you want to perform a flashback query, you need to set the following three parameters! 1.alter system set undo_management = auto; 2.alter system set undo_retention = 86400; 3.Grant Execute on dbms_flashback to username; undo_retrion parameter unit is Seconds if this value is set, such as 1 day, if the database is more frequent, the undo space will require a larger
