SQL & PL/SQL

Hello Gents and Gals,

I am been tasked to find out when the last time someone updated the data in a table.

Now, I know how to find out the last time a table has had DDL changed on it.

Like this here:

select OBJECT_NAME,LAST_DDL_TIME from dba_objects where OBJECT_NAME = 'tablename';

But, How can you determine what user updated what "data" inside the table?

Thanks,

Lady Allora...