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From Tomás Tormo <>
Subject Tomcat and database connection
Date Thu, 13 May 2010 08:35:21 GMT

I would like to understand correctly how Tomcat database pool works.

As I understand, when the application starts, a pool connection is 
created with *initialSize* connections (0 by default).

Later on, new connections are created on demand of the application, 
untill it reaches the *maxActive* connections. If *maxActive* has been 
reached and the application requests for a new connection, the pool will 
wait *maxWait* milliseconds for a free connection.

If any connection has been released, it will be kept as idle as long as 
*maxIdle* is not reached. No more connections will be created if there 
are *minIdle* or more connections in the pool in idle state.

¿Am I right?

But I still have some questions:

¿How to see the pool connection state in real time? (idle connections, 
active connections, etc). We are using Introscope for monitoring an 
application, and we can see some stalled connections... but the 
maxActive parameter is far bigger (100) than the actived connections 
shown by Introscope (24). This is happening with Tomcat 5.5 on CentOs 
using Java 1.6.

Thank you very much

Un saludo,

Tomás Tormo Franco
Area de sistemas

C/ Dels Traginers 14, 2º B
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46014 Valencia
Tel. (34) 96 381 99 47
Fax. (34) 96 381 99 48

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