Which two are true about monitoring waits for sessions and services?

The correct answer is A. V$SERVICE_EVENT displays wait counts for every wait event for each service even including C. V$SESSION_WAIT and V$SESSION both contain details of the event on which a waiting. Option A is correct because V$SERVICE_EVENT tracks cumulative wait event statistics per service and includes all wait events - even idle wait events - giving a comprehensive picture of what each service has waited on since instance startup. Option C is correct because both…

Monitoring and Tuning

Question

Options

AV$SERVICE_EVENT displays wait counts for every wait event for each service even including
BV$SESSION_WAIT and V$SESSION both contain details of the event on which a non-waiting
CV$SESSION_WAIT and V$SESSION both contain details of the event on which a waiting
DV$SESSION_EVENT displays all waits events for those events that have occurred at least
EV$SESSION_WAIT_CLASS displays waits broken down by wait class only for terminated

How the community answered

(43 responses)

A
84% (36)
B
2% (1)
D
5% (2)
E
9% (4)

Explanation

Option A is correct because V$SERVICE_EVENT tracks cumulative wait event statistics per service and includes all wait events - even idle wait events - giving a comprehensive picture of what each service has waited on since instance startup.

Option C is correct because both V$SESSION_WAIT and V$SESSION expose current wait event details (event name, wait time, p1/p2/p3 parameters) for sessions that are actively waiting, making them redundant but consistent sources for diagnosing live waits.

Why the distractors are wrong:

B is the mirror of C but says "non-waiting" - V$SESSION does preserve the last wait event for idle sessions, but V$SESSION_WAIT is specifically oriented toward current/active waits, so claiming both fully describe non-waiting session details is inaccurate.
D likely claims V$SESSION_EVENT covers events that have never fired or misrepresents its scope - in reality it shows per-session cumulative stats only for events that have occurred at least once, so "all wait events" is too broad.
E incorrectly ties V$SESSION_WAIT_CLASS to terminated sessions; it shows wait-class breakdowns for current sessions only, not historical or ended ones.

Memory tip: Think Service = Sweeping (A collects everything including idle); Session + Wait = Watching live action (C = both views agree on what's happening right now). The wrong answers either flip "waiting/non-waiting" (B vs C), overstate scope (D), or misassign the view to dead sessions (E).

Topics

#Performance Monitoring#Dynamic Performance Views#Session Waits#Wait Events

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