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From: Jeffrey Janner <Jeffrey.Janner@PolyDyne.com>
To: 'Tomcat Users List' <users@tomcat.apache.org>, "'chris@derham.me.uk'"
	<chris@derham.me.uk>
Subject: RE: Tomcat 7.0.28 connection pool issue
Thread-Topic: Tomcat 7.0.28 connection pool issue
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Date: Thu, 28 Jun 2012 20:33:39 +0000
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> -----Original Message-----=0D=0A> From: cjderham@gmail.com [mailto:cjderh=
am@gmail.com] On Behalf Of chris=0D=0A> derham=0D=0A> Sent: Thursday, June =
28, 2012 10:47 AM=0D=0A> To: Tomcat Users List=0D=0A> Subject: Re: Tomcat 7=
=2E0.28 connection pool issue=0D=0A>=20=0D=0A> On Thu, Jun 28, 2012 at 12:3=
8 PM, Yasser <yarafatin@gmail.com> wrote:=0D=0A>=20=0D=0A> > Yes. It does s=
how that maxactive has reached 100. I also use splunk=0D=0A> to=0D=0A> > ge=
t the connection status at the oracle side.=0D=0A> > What I dont understand=
 is that Resin needs just 50 connections to=0D=0A> > handle the same load. =
I am in the process of increasing the count to=0D=0A> > 300 and see if that=
 makes a difference. Oracle has the capacity to=0D=0A> > handle that many c=
onnections.=0D=0A> >=0D=0A> > We hit an odd oracle exception that may be re=
lated. Can't explain it=0D=0A> really well, but the essence of the bug in O=
racle was that the=0D=0A> tnslistener's connection count wasn't updated "re=
gularly enough" when=0D=0A> connections closed, so it could believe that th=
e connection limit had=0D=0A> exceeded when the db instance was still happy=
 to accept more=0D=0A> connections.=0D=0A> As I recall this was a known Ora=
cle issue, and was fixed by increasing=0D=0A> the acceptable connection cou=
nt in Oracle. Can you provide the exact=0D=0A> exception from the logs that=
 you hit=3F=0D=0A=0D=0AChris, this is one of the reasons for using a pool. =
 Since the physical DB connection between Tomcat & Oracle is never actually=
 closed in a pool scenario, you don't run into this problem (unless, of cou=
rse, you have some other app also connection to the DB and not using a conn=
ection pool).=0D=0AIt's a function of how Oracle is designed, the Listener =
adds one to the "open" count for each new connection, and then hands the co=
nnection off to another process.  At this point, the Listener no longer car=
es about the connection, and is not involved in "closing" the connection. T=
here is another Oracle process that periodically updates the Listener with =
the actual current count of connections.  I'm not sure what the "periodical=
ly" is set to, something like 10/15 seconds. Think of it as analogous to th=
e TIMED-WAIT status of TCP connections (something that also easy to get cau=
ght up in without a connection pool).=0D=0A=0D=0AJeff=0D=0A=5F=5F=5F=5F=5F=5F=
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=
=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=5F=0D=0A=0D=0AConfident=
iality Notice:  This Transmission (including any attachments) may contain i=
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ng of this communication is strictly prohibited. =20=0D=0A=0D=0AIf you have=
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