At 5：30 PM， a database administrator， William， is informed that an important record of employee no E0025 is missing from the SCOTT.EMPLOYEE table. At 4：30 P.M， the table contained the record of employee no E0025. William issues the following command to find the SQL statements that are used to undo the deletion：   
SELECT operation， undo_sql， logon_user  
FROM FLASHBACK_TRANSACTION_QUERY  WHERE xid=  
HEXTORAW（’0100043E23456’）；  
where ’0100043E23456’ is the transaction ID of the transaction that deleted the row. Before issuing the above statement， which task did William perform to identify the transaction ID of the transaction that deleted the row？（）