user_tab_modifications

USER_TAB_MODIFICATIONS describes modifications to all tables owned by the current user that have been modified since the last time statistics were gathered on the tables

1.SQL> select * from user_tab_modifications;

no rows selected

2.SQL> insert into t values(1);

3.commit;

4.SQL> select * from user_tab_modifications;

no rows selected

why? because you need to wait for a moment,or you have'd executed the procedure dbms_stats.flush_database_monitoring_info().

5.exec dbms_stats.flush_database_monitoring_info()

6.

SQL> select * from user_tab_modifications;

you will get the expected result.