RE: Caught YAPPing
Raj,
You can of course compute the average any list of numbers. However, if
your list contains data from fundamentally different types of data, then
your average will be meaningless. Example:
A = {Response times for program 'a'} = {20:58.13, 42:19.28, 34:11.23}
B = {Response times for program 'b'} = {00:00.79, 00:00.42, 00:00.65}
Then we have:
Mean(A) = 1,949.547 seconds
Mean(B) = 0.620 seconds
Mean(A union B) = 975.083 seconds
So the real question is does Mean(A union B) really mean anything? The
answer is no, because A and B come from radically different
distributions. If you want to see some real problems here, imagine what
happens when B has 15,000 elements in it per day and A has 20 per day.
What does the combined average tell you? Nothing much, really, except
for contrivances like...
* If on consecutive days, Count(A) = Count(B), but Mean(A union B)
changed dramatically, then something interesting has happened.
This type of phenomenon is an important part of the reason why any
method that uses count-based ratios (i.e., hit ratios) to tune a
database is an unreliable method.
On the other hand, if you're recording response times for only a single
particular type of transaction (e.g., one list only for A, and another
list only for B), then the averages (Mean(A) and Mean(B)) should be
extremely instructive. The important thing is that you have to segment
your transactions into different lists.
For response times, the criterion for splitting a list like A union B
into separate lists like A and B is that the data in each individual
list should fit the so-called exponential distribution. To figure out
whether a given list fits that distribution, you can either dust off
your old statistics books, or you can wait until about June and use the
Perl code that'll be supplied in the Optimizing Response Time book
(O'Reilly) I'm working on.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
Upcoming events:
- 2003 Hotsos Symposium, Feb 9-12 Dallas
- RMOUG Training Days 2003, Mar 5-6 Denver
- Hotsos Clinic 101, Mar 26-28 London
-Original Message-
[EMAIL PROTECTED]
Sent: Thursday, January 16, 2003 12:24 PM
To: Multiple recipients of list ORACLE-L
Hello Everyone,
Is there anything, called an Average Response Time for an Oracle
database? I got a request from one of the application owners as under :
Snip
If I can get a log of AVERAGE response time for 1/2 hour periods
starting
at 9am and running thru 5 pm I would be in heaven. If I cannot get
this,
what would be of similar help. Here is an example of what I would like
to
see, say, for today:
Time Average Response time
9-9:30 2.3 sec
9:30-10 3.0 sec
10-10:303.3 sec
10:30-113.3 sec
11-11:304.5 sec
and so on (one report for each day)
When we get to 10 seconds we have trouble. If we have spikes we can try
to
figure out why. ALso, the cost of the above would be a factor. We
have
NO money for this.
End Snip
How can I get this from system or session wait tables or v$sysstat? Any
ideas?
Regards
Raj
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RE: Caught YAPPing
Thank You for your response Cary. You say The important thing is that you
have to segment your transactions into different lists. I did convey
something similar to the requestor. I have now put the ball back in their
court, by telling them to identify some crucial functions or precise
statements that they would need to monitor as such. I dont expect to hear
back from them.
Anyways, this is a request from the management, and they like to see things
in graphs with spikes, and ratios. I got a crude way to do this for now. I
am presently capturing some baseline, acceptable wait times for some of the
key wait events. I then plan to utilize statspack to take snapshots every
hour, and code for scripts to query the underlying tables. If anything
exceeds the accepted values, shoot out alerts. Then, I plan to use the
statsviewer tool (http://www.geocities.com/alexdabr/spstd.html)
Thank you for your insight. I look forward to the book.
Raj
Cary Millsap
cary.millsap@hTo: Multiple recipients of list
ORACLE-L [EMAIL PROTECTED]
otsos.com cc:
Sent by: Subject: RE: Caught YAPPing
[EMAIL PROTECTED]
m
January 17,
2003 01:50 PM
Please respond
to ORACLE-L
Raj,
You can of course compute the average any list of numbers. However, if
your list contains data from fundamentally different types of data, then
your average will be meaningless. Example:
A = {Response times for program 'a'} = {20:58.13, 42:19.28, 34:11.23}
B = {Response times for program 'b'} = {00:00.79, 00:00.42, 00:00.65}
Then we have:
Mean(A) = 1,949.547 seconds
Mean(B) = 0.620 seconds
Mean(A union B) = 975.083 seconds
So the real question is does Mean(A union B) really mean anything? The
answer is no, because A and B come from radically different
distributions. If you want to see some real problems here, imagine what
happens when B has 15,000 elements in it per day and A has 20 per day.
What does the combined average tell you? Nothing much, really, except
for contrivances like...
* If on consecutive days, Count(A) = Count(B), but Mean(A union B)
changed dramatically, then something interesting has happened.
This type of phenomenon is an important part of the reason why any
method that uses count-based ratios (i.e., hit ratios) to tune a
database is an unreliable method.
On the other hand, if you're recording response times for only a single
particular type of transaction (e.g., one list only for A, and another
list only for B), then the averages (Mean(A) and Mean(B)) should be
extremely instructive. The important thing is that you have to segment
your transactions into different lists.
For response times, the criterion for splitting a list like A union B
into separate lists like A and B is that the data in each individual
list should fit the so-called exponential distribution. To figure out
whether a given list fits that distribution, you can either dust off
your old statistics books, or you can wait until about June and use the
Perl code that'll be supplied in the Optimizing Response Time book
(O'Reilly) I'm working on.
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
Upcoming events:
- 2003 Hotsos Symposium, Feb 9-12 Dallas
- RMOUG Training Days 2003, Mar 5-6 Denver
- Hotsos Clinic 101, Mar 26-28 London
-Original Message-
[EMAIL PROTECTED]
Sent: Thursday, January 16, 2003 12:24 PM
To: Multiple recipients of list ORACLE-L
Hello Everyone
RE: Caught YAPPing
Rajesh: You can schedule statspack snaps at 30 minutes interval and then compare the response times at each interval.. But the question is 'what do you mean by average response time?' KG Best Regards, K Gopalakrishnan -Original Message- [EMAIL PROTECTED] Sent: Thursday, January 16, 2003 10:24 AM To: Multiple recipients of list ORACLE-L Hello Everyone, Is there anything, called an Average Response Time for an Oracle database? I got a request from one of the application owners as under : Snip If I can get a log of AVERAGE response time for 1/2 hour periods starting at 9am and running thru 5 pm I would be in heaven. If I cannot get this, what would be of similar help. Here is an example of what I would like to see, say, for today: Time Average Response time 9-9:30 2.3 sec 9:30-10 3.0 sec 10-10:303.3 sec 10:30-113.3 sec 11-11:304.5 sec and so on (one report for each day) When we get to 10 seconds we have trouble. If we have spikes we can try to figure out why. ALso, the cost of the above would be a factor. We have NO money for this. End Snip How can I get this from system or session wait tables or v$sysstat? Any ideas? Regards Raj -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: K Gopalakrishnan INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
