A user, SCOTT, complains that his database session, SID 249, is extremely slow in processing
transactions. You check the ADDM report and do not find any overall database performance issues.
You decide to check the wait events, specifically in SCOTT’s session and issue the following command:
SQL>SELECT wait_class_id, wait_class, total_waits, time_waited
FROM v$session_wait_class
WHERE sid = 249;
View Exhibit1 and examine the output.
You note that the APPLICATION wait class is the second most expensive wait class after the IDLE
wait class.
You issue the following query to identify individual waits in the APPLICATION wait class:
SQL>select event, total_waits, time_waited
from v$system_event e, v$event_name n
where n.event_id = e.event_id
and wait_class_id = 4217450380;
View Exhibit2 and examine the output.
Which view would you examine next to pinpoint the problem that is causing this performance issue?
A.
DBA_HIST_SESSMETRIC_HISTORY – to find the highest value metrics in the session
B.
V$SQLAREA statistics – to find the SQL statements with the highest number of executions
C.
V$SESS_TIME_MODEL – to identify whether the SQL statements in the session were spending
more of execution time in parsing or waiting for the CPU
D.
V$EVENT_HISTOGRAM – to determine whether the TIME_WAITED is evenly distributed
across the occurrences of the wait or whether some waits for the events were very long whilst
others were short indicating more erratic response times.
enq: TX – row lock contention is the transaction lock
echo V$EVENT_HISTOGRAM to see if the wait is evenly distributed or not.
D is right