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Application Performance advice please?

P: n/a
Hello all,

I've been recruited to assist in diagnosing and fixing a performance problem
on an application we have running on SQL Server 7.
The application itself is third party software, so we can't get at the
source code. It's a Client Management system, where consultants all over
the
country track their client meetings, results, action plans, etc. , and has
apparently been problematic for a long time now. I came into this
investigation
in mid-stream, but here's the situation as I understand it:

We have users reporting it's slow, with no discernable pattern with respect
to what part of the application they're using or now particular time of day.
I am told that it doesn't appear to be a bandwith or computer resource
problem. They apparently added two app servers a year or so ago, which
temporarily
improved the performance. We're using a nominal percentage of CPU and
memory.

There are three large tables (approx 8 million rows) that are queried often,
as users click to see their calendar of appointments or review past meetings
with a client, etc. The activity on these tables is over 90% reads
(SELECTS) with about 10% INSERTS/UPDATES. We have attempted to run the Index
Analyzer Wizard twice
but so far it just seems to hang (it could be that the workload file is too
big?) . So, what we're doing now is isolating the SELECT statements that
take a long time to run and manually comparing them to the indexes that
exist on these large tables. Since we can't alter the SQL source code,
we're trying to alter the indexes to improve performance.

What I would like to know is, is there a good way to get benchmark
measurements so we can explicitly measure any performance changes? Also, do
you think
we're going about this the right way, or is there some other avenue we could
be looking at to improve performance?

I recognize that performance questions are tricky to post/answer in a
newsgroup, because usually you need more information than is provided. The
problem is
that this is a high profile investigation (they're hauling us into meetings
every two days to report our progress) and I need to be able to convincingly
state that we have either improved performance by X% , or that it is the
application itself that's the problem and we're stuck with it.

Any thoughts would be deeply appreciated.

Thanks and best regards,

Steve
Jul 20 '05 #1
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5 Replies


P: n/a

"Steve_CA" <st********@yahoo.com> wrote in message
news:35********************@news20.bellglobal.com. ..
Hello all,

I've been recruited to assist in diagnosing and fixing a performance
problem
on an application we have running on SQL Server 7.
The application itself is third party software, so we can't get at the
source code. It's a Client Management system, where consultants all over
the
country track their client meetings, results, action plans, etc. , and has
apparently been problematic for a long time now. I came into this
investigation
in mid-stream, but here's the situation as I understand it:

We have users reporting it's slow, with no discernable pattern with
respect
to what part of the application they're using or now particular time of
day.
I am told that it doesn't appear to be a bandwith or computer resource
problem. They apparently added two app servers a year or so ago, which
temporarily
improved the performance. We're using a nominal percentage of CPU and
memory.

There are three large tables (approx 8 million rows) that are queried
often,
as users click to see their calendar of appointments or review past
meetings
with a client, etc. The activity on these tables is over 90% reads
(SELECTS) with about 10% INSERTS/UPDATES. We have attempted to run the
Index
Analyzer Wizard twice
but so far it just seems to hang (it could be that the workload file is
too
big?) . So, what we're doing now is isolating the SELECT statements that
take a long time to run and manually comparing them to the indexes that
exist on these large tables. Since we can't alter the SQL source code,
we're trying to alter the indexes to improve performance.

What I would like to know is, is there a good way to get benchmark
measurements so we can explicitly measure any performance changes? Also,
do
you think
we're going about this the right way, or is there some other avenue we
could
be looking at to improve performance?

I recognize that performance questions are tricky to post/answer in a
newsgroup, because usually you need more information than is provided.
The
problem is
that this is a high profile investigation (they're hauling us into
meetings
every two days to report our progress) and I need to be able to
convincingly
state that we have either improved performance by X% , or that it is the
application itself that's the problem and we're stuck with it.

Any thoughts would be deeply appreciated.

Thanks and best regards,

Steve


Your first stop should probably be Profiler, where you can gather lots of
information about the TSQL being executed on the server, along with
durations, I/O cost, query plans etc. And of course Perfmon for checking if
MSSQL is hitting I/O or CPU limits - if you've just joined the
investigation, you should probably satisfy yourself about that, especially
if you're now the person more or less responsible for resolving the
situation.

If it's a third-party app, then it's going to be awkward to find a
resolution, as you say. Indexes are probably the only thing you can change,
any even then you might find you've invalidated your support agreement by
doing so. But certainly, gathering information and establishing where the
bottleneck is (if there is one) should be the first step.

Simon
Jul 20 '05 #2

P: n/a
On Mon, 11 Oct 2004 08:34:12 -0400, Steve_CA wrote:
We have users reporting it's slow, with no discernable pattern with respect
to what part of the application they're using or now particular time of day.


Hi Steve,

In addition to Simon's suggestion, I'd look into possible locking problems
as well. Just add locking events to the Profiler trace already suggested
by Simon.

Best, Hugo
--

(Remove _NO_ and _SPAM_ to get my e-mail address)
Jul 20 '05 #3

P: n/a
Can you capture some of the queries that run slowly ? I imagine that a
number of them will consistently perform slowly. If so, try running
these through QA and look at the execution plan. It should indicate
where the performance hit is. You may find that this is table scans
etc...

Also, you should run the index analysis against these 'common' queries
to see if it comes up with any suggestions.

If it's locking/blocking then
http://www.sommarskog.se/sqlutil/aba_lockinfo.html will likely be of
some help

Finally, a bit of a long shot as it sounds similar to a problem we
had.

Are any views used ? Can these be improved by swapping to tables
populated by stored procedures ? You can keep the naming the same but
swap them over. To give you an example, we had 4 views which were
referenced by a final view (all were complex). Our app needed to look
at the data, but I didn't want to change the code. I swapped the view
to a table which was generated by a copy of the original view from an
SP. This saved a lot of time (1 min from startup down to 5 seconds)
with the SP being run every 10 mins on the server. This combined with
better indexing and it's saving an hour a day for them. OK, it's a
quick overview, but I'd see if you can get away with any little tricks
like this (especially if in certain circumstances you only need to
read the data). Might be worth a try.

Ryan

Hugo Kornelis <hugo@pe_NO_rFact.in_SPAM_fo> wrote in message news:<gh********************************@4ax.com>. ..
On Mon, 11 Oct 2004 08:34:12 -0400, Steve_CA wrote:
We have users reporting it's slow, with no discernable pattern with respect
to what part of the application they're using or now particular time of day.


Hi Steve,

In addition to Simon's suggestion, I'd look into possible locking problems
as well. Just add locking events to the Profiler trace already suggested
by Simon.

Best, Hugo

Jul 20 '05 #4

P: n/a
Thank you all,

Ryan, your suggestion regarding views is very relevant....one of the main
culprits is a commonly used view
and I thought we were dead in the water with version 7 (I know you can
create indexes on views in 2000).

"Ryan" <ry********@hotmail.com> wrote in message
news:78*************************@posting.google.co m...
Can you capture some of the queries that run slowly ? I imagine that a
number of them will consistently perform slowly. If so, try running
these through QA and look at the execution plan. It should indicate
where the performance hit is. You may find that this is table scans
etc...

Also, you should run the index analysis against these 'common' queries
to see if it comes up with any suggestions.

If it's locking/blocking then
http://www.sommarskog.se/sqlutil/aba_lockinfo.html will likely be of
some help

Finally, a bit of a long shot as it sounds similar to a problem we
had.

Are any views used ? Can these be improved by swapping to tables
populated by stored procedures ? You can keep the naming the same but
swap them over. To give you an example, we had 4 views which were
referenced by a final view (all were complex). Our app needed to look
at the data, but I didn't want to change the code. I swapped the view
to a table which was generated by a copy of the original view from an
SP. This saved a lot of time (1 min from startup down to 5 seconds)
with the SP being run every 10 mins on the server. This combined with
better indexing and it's saving an hour a day for them. OK, it's a
quick overview, but I'd see if you can get away with any little tricks
like this (especially if in certain circumstances you only need to
read the data). Might be worth a try.

Ryan

Hugo Kornelis <hugo@pe_NO_rFact.in_SPAM_fo> wrote in message

news:<gh********************************@4ax.com>. ..
On Mon, 11 Oct 2004 08:34:12 -0400, Steve_CA wrote:
We have users reporting it's slow, with no discernable pattern with respectto what part of the application they're using or now particular time of
day.
Hi Steve,

In addition to Simon's suggestion, I'd look into possible locking problems as well. Just add locking events to the Profiler trace already suggested
by Simon.

Best, Hugo

Jul 20 '05 #5

P: n/a
Steve,

Got your e-mail (replied directly as well). Essentially, that's what I
meant. Posting in NG in case it helps someone else later.

The scenario that we had with this was that we had a view which gathered
the data from 4 other views. Each of the 4 underlying views were a
little complex and took a while to run. Combined in the ‘top level’
view, the performance was slow. The application ran a simple summary
query of the top level view when opening. This took about 50 seconds to
run which was unacceptable to the users.

Imagine… (obviously change the names to something more meaningful)

myView1, myView2, myView3, myView4 all feed into myTopView. The
application looks to query the object myTopView.

I renamed the view from myTopView to myTopViewFull.

I created a table called myTopViewTable (the same name as the view and
the same structure as the data returned from the original view –
myTopView).

Then I created a view called myTopView (same name as my original top
level view) which pointed to the table myTopViewTable instead of the 4
lower level views. Simple ‘select *’ will do it.

All I had to do was a very simple SP which truncated the table
myTopViewTable and inserted the data from myTopViewFull. This still took
a while to run, but it only takes the hit on the server and the user
perception is changed and they think it’s run quicker. Instead of a
bunch of users all doing the same thing at a 50 second cost to each of
them, we only have a 50 second cost on the server every 10 minutes.

For our needs, it doesn’t matter for this data if we update it every 10
minutes, but the difference to the users was quite noticeable. The time
to open the application dropped from 50 seconds plus to consistently
lower than 5 seconds. I did add some indexes to the main tables
(referenced by the view) to try and speed things up and it helped a
little. I found more performance improvements in the application though
as a result.

The main benefit of this is shifting the perception of work from the
users to the server. You can also try using OPTION (NO LOCK) on the
select statements to reduce locking / blocking issues as you are taking
the data into a table directly.

Also, as SQL tables / views cannot have the same name, if you have a
view that runs far too slowly, you can sometimes get a bit of a
performance advantage by doing this. It’s crude, but it works provided
you apply it correctly. No changes to the application should be needed.

A simple test is, drop the data from the view into a table. Try a query
that you know takes a while against the view and against the table. See
if there is a performance improvement. Oh, and you could try indexes on
the new table provided you don’t take a hit re-building them.

Indexed views are possibly another option though.

Hope that helps

Ryan

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Jul 20 '05 #6

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