Pooled database connections are not being closed properly

Question

We are using WLS 9.2 and Microsoft SQL Server 2005 (version 1.1 of the Microsoft JDBC driver), and we are experiencing some strange behavior with the lifecycle of the connections in our data source pools. The WLS console may report that the current capacity of a pool is 5, but the database monitoring tools report that we have more than 5 connections open. It almost seems as though connections are getting dropped somehow and WLS thinks it has closed them and created new ones, but the original connections are never actually closed in the database. Our application is the only thing connecting to the DBMS instance in question, so the connections we are seeing have definitely been created by WebLogic. Any suggestions for tracking down the source of this problem would be greatly appreciated.
Regards,
Sabrina

Answer 1

SabrinaL wrote:
Thank you for your help. Here is our pool configuration (NOTE: Even though we're not using Oracle, we actually did create our own empty "DUAL" table to use for testing connections):
<jdbc-connection-pool-params>
<initial-capacity>10</initial-capacity>
<max-capacity>10</max-capacity>
<shrink-frequency-seconds>0</shrink-frequency-seconds>
<test-frequency-seconds>0</test-frequency-seconds>
<test-connections-on-reserve>true</test-connections-on-reserve>
<test-table-name>DUAL</test-table-name>
</jdbc-connection-pool-params>
I'm not sure exactly when the problem starts occurring because we only recently
noticed it; as far as we can tell, it's pretty random. We have seen occasional
application errors where it appears that the app cannot obtain a connection from
the pool, but I'm not sure if that issue is directly related to this particular
problem. We were careful to scale our pool size such that it should always have
enough connections, so I'm not sure how this is possible. We are running a cluster.
Regards,
SabrinaOk, then for every server in the cluster, the server will make 10 connections.
Because you are using SQLServer, your 'test table' (that is an overloaded
field) should be set to actually define SQL that we can use for a quick test:
<test-table-name>SQL select 1</test-table-name>
That will be quicker than selecting from any real table.
We would need more info about the problem. If you turn on
JDBC logging, we might capture the exceptions that indicate
problems with the pool, however, as configured, the pools
will have only 10 connections, and will close and replace
any that fail the test. Do you have a firewall between the
DBMS and WebLogic?
Joe