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From Jeremy Arnold <>
Subject Re: JDBC sampler - connection pool
Date Fri, 05 Sep 2003 21:13:31 GMT
    "Number of Connections in Pool" is the number of database 
connections which will be created.  These connections get put in a pool, 
and each request will grab a connection from the pool, use it, and then 
put the connection back in to the pool.

    "Max Usage For Each Connection" is the maximum number of times that 
a connection will be used.  Once this limit has been hit, the connection 
will be closed and a new one will be opened to replace it.  A large 
value is probably best, as closing and opening database connections is 
rather expensive.  Some databases and/or JDBC drivers may encounter 
problems (either functional problems or reduced performance) if you keep 
the connection open for too many requests though.  So you may have to 
experiment a bit.

    I haven't personally tried using the default config elements with a 
JDBC sampler, but I've heard one or two reports recently that it doesn't 
work.  I've been doing some development with the JDBC sampler recently, 
so when I get a bit of time I'll take a look at it.  It could be a few 
weeks though...I'm moving at the end of this month, and don't have a lot 
of spare time right now.

    I haven't really noticed the behavior you described where only one 
active connection is used, but I haven't really been looking out for 
that kind of issue.  So I'd have to check a few things before I could 
tell you whether it is a bug in JMeter or if it is something else.  I'll 
try to look into that too when I get a chance.


Ryszard Lach wrote:

>I'm trying to test my postgresql database using jmeter. I have created a
>thread group with a couple of (ca. 100) jdbc samplers (under one random
>controller). Everything works fine, but I cannot understand what is the
>meaning of "Number of Connections in Pool" and "Max Usage For Each
>Connection" in "JDBC Database Connection Pool defaults" and in "JDBC
>Normally (i.e. with http samplers) one can leave a field blank knowing
>it will be filled with value defined in default config element, but with
>JDBC Sampler it doesn't work. Why?
>The other thing: I suppose, that setting number of connections to 5 and
>max usage to a large value  - I will have 5 concurrent connections
>between jmeter and database still open and used by testing threads.
>Unfortunately, I see one active connection. Thus increasing number of
>threads from 5 to 10 - I can not observe bigger load on database server.
>Could the random controller be the cause of such a behaviour? All in
>all, each single test contains only one (random) request. 

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