Hi all, another quick as reference. Table statistics as everyone knows are very important when the CBO is creating the execution plan. When you have new statistics Oracle will invalid the current execution plans affected by them and create new execution plans based on the new statistics. Most of the time it gets right if that causes your execution plan to change for worse?
In this situations dba_tab_stats_history view and dbms_stats.restore_table_stats procedures are your friends.
To validate set and check and set the stats history:
select dbms_stats.get_stats_history_retention from dual; exec dbms_stats.alter_stats_history_retention(30);
On dba_tab_stats_history you can view the last statistics available:
select table_name, stats_update_time, from dba_tab_stats_history where table_name='TABLE1' and owner='USER' order by 2 desc;
Use the dbms_stats.restore_table_stats to restore the statistics:
exec dbms_stats.restore_table_stats(ownname=>'USER',tabname=>'TABLE1',AS_OF_TIMESTAMP=>'DATE from column STATS_UPDATE_TIME on dba_tab_stats_history');
Hope it helps!