To filter data by SCN (system change number), use the STARTSCN and ENDSCN parameters to the PL/SQL DBMS_LOGMNR.START_LOGMNR procedure, as shown in this example:
EXECUTE DBMS_LOGMNR.START_LOGMNR(-
STARTSCN => 621047, -
ENDSCN => 625695, -
OPTIONS => DBMS_LOGMNR.DICT_FROM_ONLINE_CATALOG + -
DBMS_LOGMNR.CONTINUOUS_MINE);
The STARTSCN and ENDSCN parameters override the STARTTIME and ENDTIME parameters in situations where all are specified.
"Examples Using LogMiner" for a complete example of filtering data by SCN
Oracle Database PL/SQL Packages and Types Reference for information about what happens if you specify starting and ending SCN values and they are not found in the LogMiner redo log file list and for information about how these parameters interact with the CONTINUOUS_MINE option