Look for an invalid index ?
- it may have used an index lookup for this yesterday, and is doing FTS
today ?
Checking the explain plan will reveal ...
-----Original Message-----
From: JAIMURUGAN Shanmuga Velayutham
[mailto:oracledba-ezmlmshield-x23705609.[Email address protected]
Sent: 31 May 2005 11:18
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
Confidentiality Statement:
This message is intended only for the individual or entity to which it is
addressed. It may contain privileged, confidential information which is
exempt from disclosure under applicable laws. If you are not the intended
recipient, please note that you are strictly prohibited from disseminating
or distributing this information (other than to the intended recipient) or
copying this information. If you have received this communication in error,
please notify us immediately by return email.
--------
website: http://www.LazyDBA.com
Please don't reply to RTFM questions
Oracle documentation is here: http://tahiti.oracle.com
To unsubscribe: see http://www.lazydba.com/unsubscribe.html
To subscribe: see http://www.lazydba.com
By using this list you agree to these
terms:http://www.lazydba.com/legal.html
Feel better with BUPA
Visit http://www.bupa.com or call 0800 00 10 10 and find out what BUPA can do for you.
BUPA House 15-19 Bloomsbury Way London WC1A 2BA
Internet communications are not secure and therefore BUPA does
not accept legal responsibility for the contents of this message. Any
views or opinions presented are solely those of the author and do
not necessarily represent those of BUPA.
BUPA Insurance Limited, BUPA Health Assurance Limited, BUPA Insurance Services Limited and Goldsborough Estates Limited are authorised and regulated by the Financial Services Authority
Oracle LazyDBA home page