2009-08-03

ORACLE WAITS

TIME_STATISTICS = true

v$event_name #describe events with parameters P and share to 12 wait_class

v$system_event #based on events which was collected when instance was started for all sessions (please check TIME_WAITED regard to  STARTUP_TIME.v$instance)
  • TOTAL_WAITS #how many times session was waiting on this event
  • TOTAL_TIMEOUTS #how often default time was reached, default time is set for each event
  • TIME_WAITED # time used by event (1/100 sek)
  • TIME_WAITED_MICRO #as above (/1000000 sek)
  • AVERAGE_WAIT #average time TIME_WAITED/TOTAL_WAITS (1/100 sek)
v$session_event #the same as v$system_event but for session, added SID column

v$session_wait #present events which was expected by session
  • SEQ #internal seqence nr for any event, it is increased any time when session wait at event
  • STATE #value WAITING and WAITED UNKNOWN TIME show that TIMES_STATISTICS is FALSE
  • SECONDS_IN_WAIT #time spending by session

from 10g
v$session_wait_history #the same as v$session_wait but there is last 10 wait events for any session but col SEQ# means something diferent
v$active_session_history #last 30 min probes which was collected every 1 sec., more probes than at v$session_wait_history

v$system_wait_class #waits grouped by class category
v$session_wait_class #waits grouped by class and session category

v$event_histogram #share between events which spend less than 1,2,4,8,16 ms