USER_TAB_MODIFICATIONS not getting populated automatically

Question

Hi All,
I am in the process of setting up gathering of schema statistics on my database and was trying to setup estimate stale statistics based on the data from the USER_TAB_MODIFICATONS table. Although I see that monitoring has been turned ON for all the tables in the DB and DML operations are also being carried out on a daily basis, the USER_TAB_MODIFICATIONS remains empty all the time.
I tried executing DBMS_STATS.FLUSH_DB_MONITORING_INFO so as to get this table populated. As soon as i executed it, i could see that the records for all the transactions carried out on that schema during the day appeared in the USER_TAB_MODIFICATIONS table. However, when i again carried out a DML operation as waited for 3 hrs so that it would get populated automatically in the table, I could not see any rows for that table in user_tab_modifications.
Can anyone help me out with what could possibly be the reason behind it? Maybe some background process that populated the user_tab_modifications every 3 hours is disabled? Or is there any other reason behind it?
Please advice.

Answer 1

CrazyAnie,
Here is an illustration for you;
SQL> set line 1000
SQL> set pagesize 1000
SQL> drop table ogan_deneme purge;
drop table ogan_deneme purge
ERROR at line 1:
ORA-00942: table or view does not exist
SQL> create table ogan_deneme (deneme varchar2(10)) monitoring;
Table created.
SQL> insert into ogan_deneme values ('ogan');
1 row created.
SQL> /
1 row created.
SQL> /
1 row created.
SQL> delete ogan_deneme;
3 rows deleted.
SQL> commit;
Commit complete.
SQL> select * from user_tab_modifications;
no rows selected
SQL> exec dbms_stats.gather_table_stats('ogan','ogan_deneme');
PL/SQL procedure successfully completed.
SQL> select * from user_tab_modifications;
no rows selected
SQL> conn / as sysdba
Connected.
SQL> select * from dba_tab_modifications where table_owner = 'ogan';
no rows selected
SQL> select * from dba_tab_modifications where table_owner = 'OGAN';
no rows selected
SQL> conn ogan/password
Connected.
SQL> exec dbms_stats.gather_table_stats('ogan','ogan_deneme');
PL/SQL procedure successfully completed.
SQL> insert into ogan_deneme values('ogan');
1 row created.
SQL> /
1 row created.
SQL> /
1 row created.
SQL> delete from ogan_deneme;
3 rows deleted.
SQL> commit;
Commit complete.
SQL> select * from user_tab_modifications;
no rows selected
SQL> exec dbms_stats.FLUSH_DATABASE_MONITORING_INFO;
BEGIN dbms_stats.FLUSH_DATABASE_MONITORING_INFO; END;
ERROR at line 1:
ORA-20000: Insufficient privileges
ORA-06512: at "SYS.DBMS_STATS", line 2151
ORA-06512: at "SYS.DBMS_STATS", line 14390
ORA-06512: at line 1
SQL> conn / as sysdba
Connected.
SQL> exec dbms_stats.FLUSH_DATABASE_MONITORING_INFO;
PL/SQL procedure successfully completed.
SQL> conn ogan/password
Connected.
SQL> select * from user_tab_modifications;
TABLE_NAME PARTITION_NAME SUBPARTITION_NAME INSERTS UPDATES DELETES TIMESTAMP TRU DROP_SEGMENTS
OGAN_DENEME 3 0 3 25-JUN-10 NO 0
SQL>
Even you have executed dbms_stats.FLUSH_DATABASE_MONITORING_INFO; and so still do not see any data, gather table stats for the relevant table.
Hope it helps,
Ogan