Exam 1z0-083 topic 1 question 12 discussion

Answer: B, D, F Explanation : A, E - False : V$SESSION_EVENT displays information on waits for an event by a session. V$SESSION_WAIT_HISTORY displays the last 10 wait events for each active session. B - V$SERVICE_EVENT displays aggregated wait counts and wait times for each wait statistic. C - False : V$SESSION_WAIT_CLASS displays the time spent in various wait event operations on a per-session basis. D, F - True : V$SESSION_WAIT displays the current or last wait for each session. V$SESSION.EVENT If the session is currently waiting, then the resource or event for which the session is waiting. If the session is not in a wait, then the resource or event for which the session most recently waited. Resource : https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/V-SESSION_EVENT.html#GUID-5723D404-83F7-4C8D-8BF2-031B3FFEAAA8

The session/service views show what is happening NOW. You can append _HISTORY onto these (eg, V_SESSION_WAIT_HISTORY) to see what happened in the past, to sessions that have disconnected (on disconnect, Oracle will, basically, copy that session's v$ data into the corresponding v$_HISTORY views. Therefore, any answer that refers to anything in the past, here, must be wrong. Another note is that all sessions are ALWAYS waiting for something. An "active" wait would be waiting for I/O to return. An "idle" wait would be waiting for the user to ask the DB to do something. They're both considered to be "waits", so the DB is always waiting. A: FALSE - It shows these details for existing sessions, not past sessions. B: TRUE - The definition is exactly what the view does C: TRUE - As mentioned, all sessions are always waiting. So, this is true D: FALSE - There is no such thing as a "non-waiting session", so this must be false. E: FALSE - This references older sessions, so you would need to access the _HISTORY view for this data. F: TRUE - This is exactly what these views do. Therefore, BCF are correct

BDF D is incorrect, I think not only displays waits broken down by wait class V$SESSION_WAIT_CLASS displays the time spent in various wait event operations on a per-session basis. https://docs.oracle.com/en/database/oracle/oracle-database/19/refrn/V-SESSION_WAIT_CLASS.html#GUID-B890F027-CE8A-452B-96B2-213985B21484

The V$SERVICE_EVENT view shows, by service, the total waits for a particular event since instance startup. => B: TRUE The V$SESSION_WAIT_CLASS view aggregates the waits by session and wait class, since instance startup. All sessions are always waiting. => C: TRUE The V$SESSION_WAIT view lists the resources or events for which active sessions are waiting. The V$SESSION view also includes the current wait information. => F: TRUE & D: FALSE

Sorry for the duplicate comment, but the right question is B,D,F

B,D,F 100%

B,C,F for sure.

both V$SESSION_WAIT and V$SESSION contains information of actual wait or last wait (example: column "state" shows "waiting" or "waited for short"). C incorrect because contains statistical counts for non-waiting sessions too.

Answer: B D F

BCF is correct

BDF Sessions are not always waiting - they can be in working state (ON CPU). Check description of EVENT column: If the session is currently waiting, then the resource or event for which the session is waiting. If the session is not in a wait, then the resource or event for which the session most recently waited.

It's BCF. You're checking for current waits, not past waits.

I think C is wrong The V$SESSION_WAIT_CLASS view allows you to see the session wait information broken down by wait class for each session. https://oracle-base.com/articles/10g/performance-tuning-enhancements-10g

form me BCF are corrects

E and A incorrect? as it speaks about past sessions, i presume AWR is necessary (e.g. hist tables)

C incorrect: v$session_wait_class will also show the waits happened for non waiting sessions

BCF: V$SESSION_WAIT_CLASS displays the time spent in various wait event operations on a per-session basis. V$SESSION_WAIT displays the current or last wait for each session. V$SESSION displays session information for each current session.