Hi all,
One more question from the interview. Hoping to get some feedbacks from
the group.
Suddenly a user comes and tells you that his application is very slow,
he is not getting the output in the desired time as he would earlier. As
a DBA what will be your line of approach.
My answer to this was Go to the enterprise manager navigate through the
session through which the user connects and see whether the process is
hanging or running (You will get the status through the progress bar).
Try running the SQL from SQLPLUS if the query runs fine there may be
some problem with network .Or the execution plan for the query would
have changed suddenly due to dropping of index or whatever reason which
degrades the performance. If there is a problem with the execution plan
try and tune the query.
But this answer doesn't seem to satisfy the interviewer..
Any suggestions are highly appreciated.
Thanks in advance
JAIMURUGAN
---Original Message-----
From: JAIMURUGAN Shanmuga Velayutham
[mailto:oracledba-ezmlmshield-x23705609.[Email address protected]
Sent: Tuesday, May 31, 2005 3:48 PM
To: LazyDBA Discussion
Subject: Select Count(*) very fast yesterday but its slow today
Hi all,
This was the question recently I encountered in an interview. I gave the
answers below but that doesn't seem to satisfy the interviewer.
QUESTION:-
SELECT COUNT (*) FROM TABLE_NAME:
The query ran fine and I got the output in less than 25 seconds.
The next day I ran the same query and I got the output after 15 minutes.
What is the reason for this? As a DBA what is that you will check
immediately?
My Answer:-
1. Mass insert or mass delete would have happened in the table,
Statistics were not gathered after that .So the performance has
degraded.
2. Statistics would have been deleted.
Are there any other reasons for the performance degradation?
Thanks in advance
JAIMURUGAN
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