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From Phil Steitz <>
Subject [dbcp] RE: MaxActive and MaxIdle
Date Sat, 18 Apr 2009 20:49:15 GMT wrote:

Sorry for the delayed response.  Since this list is shared for all 
commons components, it's best to prefix the subject line, as I have 
changed it above, to include the component name.  See responses to your 
questions below.
> Hello,
> I saw someone else ask this exact same question back in Dec but the reply
> they received never really answered the question, so I thought I'd try
> again.
> I am using the dbcp included within Tomcat 5.5.27.
So should be dbcp 1.2.2,  pool 1.4
>   I configure it using
> context.xml with: maxActive="30" maxIdle="10"
> I always assumed that maxActive would limit the total amount of DB
> connections that could ever be open at one time (in this case 30). 
That is correct.
>  Yet
> from what I see it seems like I am limited to maxActive + maxIdle
> connections open (in this case 40).  Is that true?
No, maxActive should limit the total number of connections, idle in the 
pool or checked out to clients.
> Also, the default behavior seems to be that the connections never close (or
> timeout) within the pool when they are not being used. 
Yes, the default behavior is not to validate or time out connections 
while they are idle in the pool.  You can change this behavior by 
setting timeBetweenEvictionRunsMillis and minEvictableIdleTimeMillis to 
positive numbers.  The first of these determines how often (in 
milliseconds) the "idle object evictor" runs and the second (also in 
milliseconds) determines how long a connection can sit idle in the pool 
before it is eligible for "eviction."
>  I had my Tomcat
> server sit there for about an hour idle with no client requests incoming
> and when I ran netstat -a I still saw 39 connections open, they only closed
> when I killed Tomcat.  Do I have to turn on some kind of cleanup explicitly?
See comment above on timing out idle connections,  though be careful 
about setting this too aggressively as it can lead to connection churn.  
The number of open connections - 39 - looks too large for the maxActive 
setting above.   Are you sure all of the connections were opened by the 
connection pool?

> thanks!
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