AWR Collection and Check.

AWR:
Automatic Workload Repository. it collect database statistics automatically ( every 1 hour as default).

CHECK AWR SETTING:
log in as sysdab:
select snap_interval, retention, topnsql from wrm$_wr_control;

CREATE SNAPSHOT MANUALLY:
exec dbms_workload_repository.create_snapshot();

TURN OFF SNAPHOT COLLECTION:
exec dbms_workload_repository.modify_snapshot_settings(interval => 0);

TURN ON SNAPHOT COLLECTION HOURLY:
exec dbms_workload_repository.modify_snapshot_settings(interval => 60);

SYNTEX:

DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS(
   retention   IN  NUMBER    DEFAULT NULL,
   interval    IN  NUMBER    DEFAULT NULL,
   topnsql     IN  NUMBER    DEFAULT NULL,
   dbid        IN  NUMBER    DEFAULT NULL);

DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS(
   retention   IN  NUMBER    DEFAULT NULL,
   interval    IN  NUMBER    DEFAULT NULL,
   topnsql     IN  VARCHAR2,
   dbid        IN  NUMBER    DEFAULT NULL);

CHECK LASTEST COLLECTION:
select systimestamp, most_recent_snap_time, snap_interval from wrm$_wr_control where dbid = (select dbid from v$database);

CHECK ERORR COLLECTION:
select * from wrm$_snap_error
 where dbid = (select dbid from v$database)
 order by snap_id;

select * from
(select snap_id,
instance_number,
 begin_interval_time,
 end_interval_time,
 flush_elapsed,
status,
 error_count,
 snap_flag
from wrm$_snapshot
 where dbid = (select dbid from v$database)
 order by snap_id desc)
 where rownum <= 10
 order by snap_id;

TRACE AUOT SNAPHOE COLLECTION:
snapshot was automatically collected by MMON background process
MMON action trace
alter session set "_swrf_test_action"=28;
snapshot flush trace
alter session set "_swrf_test_action"=10;

trun off trace
MMON action trace
alter session set "_swrf_test_action"=29;
snapshot flush trace
alter session set "_swrf_test_action"=11;

MORE TRACE INFO:
begin
dbms_monitor.serv_mod_act_trace_enable(service_name=>'SYS$BACKGROUND',
module_name=>'MMON_SLAVE',
action_name=>'Auto-Flush Slave Action');

dbms_monitor.serv_mod_act_trace_enable(service_name=>'SYS$BACKGROUND',
module_name=>'MMON_SLAVE',
action_name=>'Remote-Flush Slave Action');
end;
/
# trace AWR snapshots
alter session set events 'immediate trace name awr_test level 1';
# trace AWR purging
alter session set events 'immediate trace name awr_test level 2';
# trace AWR SQL
alter session set events 'immediate trace name awr_test level 3';
# turn off all of the above, if set
alter session set events 'immediate trace name awr_test level 4';






reference:
metalink document: Troubleshooting: AWR Snapshot Collection issues [ID 1301503.1]
http://www.orafaq.com/forum/t/166607/0/
http://orastory.wordpress.com/2011/10/27/what-job-runs-awr-snapshot/
http://docs.oracle.com/cd/B28359_01/server.111/b28274/autostat.htm
http://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_wkrpos.htm#BACEHJJI
http://www.oracle-base.com/articles/10g/oracle-data-pump-10g.php