Are you trying to come up with a connection pool size range to occupy the box
you already own optimally?
The other possibility is coming up with the minimum number of connections that
can achieve your service level curve of latency against the load you expect to
have (plus any safety margin), then make sure the box you configure will
support that number of connections.
The former might indeed correlate with cores.
The latter correlates with more with load and service expectations.
For both there is usually a peak performance point at a lower number of
connections than most folks would guess and MUCH lower than most line managers
who typically think they are doing themselves a favor when they demand more
“slots” either in concurrent managers or connection pools.
Of course you can also optimally tune a system for batch jobs and make
interactive work nearly impossible. That can be useful at some times of day,
which calls for a planned and scheduled change in the number of connections
available in pools (as opposed to the dynamic demand based escalation of
connections which RWP thoroughly debunks.) I wrote all that so no one makes up
a “best practice” that says your number of connections should never change.
mwf
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Stephens, Chris
Sent: Wednesday, September 16, 2015 3:55 PM
To: mihajlo.tekic@xxxxxxxxx; oyvind.isene@xxxxxxxxx
Cc: oracle-l
Subject: RE: connection pool sizing
These are excellent videos (as was the PDF supplied by Oyvind). RWP group does
a good job of explaining why a large and/or varying size connection pool can be
a problem and demonstrates the benefit of reducing the size of the connection
pool and keeping the size constant.
I was looking for a rough estimate/formula for coming up with a decent initial
pool size based on relevant factors. I think that would primarily be CPU/Core
count but could include other variables.
At least now I’ll recognize the symptoms of a connection pool size problem and
know what direction to head.
Thanks!
chris
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Mihajlo Tekic
Sent: Monday, September 14, 2015 5:58 PM
To: oyvind.isene@xxxxxxxxx
Cc: oracle-l <oracle-l@xxxxxxxxxxxxx>
Subject: Re: connection pool sizing
Below are links to couple of videos, on the subject, that you could find very
useful:
Real-World Performance - 13 - Large Dynamic Connection Pools - Part 1
https://www.youtube.com/watch?v=Oo-tBpVewP4
Real-World Performance - 14 - Large Dynamic Connection Pools - Part 2
https://www.youtube.com/watch?v=XzN8Rp6glEo
Regards,
Mihajlo Tekic
On Mon, Sep 14, 2015 at 3:25 PM, Øyvind Isene <oyvind.isene@xxxxxxxxx> wrote:
This is a topic covered by the Real World Performance Group; no one does it
better explaining this. Here is one link to a recent preso I found by googling:
http://rwpt.hroug.hr/content/download/6547/107877/file/RWP2015%20part%20I.pdf
If you go to Open World, be sure to catch at least one of their sessions, it is
probably the best infotainment you get there, especially if you have a taste
for British sarcasm ;-) Also get in touch with your local user group and see if
they have invited them for 2016.
2015-09-14 23:47 GMT+02:00 Martijn Bos <maboc@xxxxxxxx>:
I think it more depends on the usage of the connections in the pool.
If all your connections, out of the pool, are always busy it is probably
wise to take numbers of CPU into account. If they are only used once in
a while I would monitor connectionpool usage.
Best Regards,
Martijn
On 14-09-15 20:57, Stephens, Chris wrote:
Are there general recommendations on initial connection pool sizing based on
the number of CPU's available to a database?
I keep seeing connection pools sized far (far!) beyond the number of CPU's
and that doesn't make any sense to me.
Chris
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