UCP WITH TOMCAT 7 AND ORACLE 11G

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17 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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UCP WITH TOMCAT 7
AND ORACLE 11G

BY VOLKER KOSTER, MT

AG

This paper describes the process of setting up a pooled data source, implemented by
Oracle’s latest JDBC architecture for pooled connections, the Universal Connection Pool UCP,
on Apache Tomcat 7 against on Oracle 11g XE database.
USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 1
1 CONTENT
2

Abstract ............................................................................................................................... 2

3

Motivation ........................................................................................................................... 2

4

Introduction ........................................................................................................................ 2

5

Software Versions ............................................................................................................... 3

6

Standard Tomcat Connection pooling ................................................................................ 3

7

Connection pooling with Oracle ......................................................................................... 3

7.1

Previous Architectures ................................................................................................. 3

7.2

Universal Connection Pool .......................................................................................... 3

7.3

Oracle’s Resident Connection Pool ............................................................................. 4

8

Setting up UCP .................................................................................................................... 5

8.1

Prequisites ................................................................................................................... 5

8.2

Datasource Configuration ............................................................................................ 5

8.3

Placing of Context.xml ................................................................................................. 7

8.4

Tomcat Resource Factories ......................................................................................... 7

8.4.1 Using a Standard Resource Factory...................................................................... 7
8.4.2 Writing a Custom Resource Factory ................................................................... 10
9

Writing a Test Servlet ........................................................................................................ 11

9.1

What the Servlet does ............................................................................................... 11

9.2

Referencing the data source in web.xml ................................................................... 12

9.3

Borrowing a Connection ............................................................................................ 13

9.4

Verifying the results ................................................................................................... 14

10

Conclusion ......................................................................................................................... 17

11

Acknowledgments ............................................................................................................. 18

12

Readings ............................................................................................................................ 18

13

About the Autor ................................................................................................................ 18



USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 2
2 ABSTRACT
This paper describes the process of setting up a pooled data source, implemented by
Oracle’s latest JDBC architecture for pooled connections, the Universal Connection Pool UCP,
on Apache Tomcat 7 against on Oracle 11g XE database.

3 MOTIVATION
Why use Oracle UCP?
This is a valid question, because you will probably have no advantage from using UCP right
away.
UCP offers a cache of pooled connections, so what?
When working with Tomcat, you automatically get connection pooling implemented by
Apache’s DBCP project out of the box. DBCP is the common denominator for a whole bunch
of databases. This is its strength but also its weakness.
UCP is Oracle specific. It works with Oracle specific features concerning high availability in
clustered database environments, the Oracle Real Application Cluster or RAC. By way of
configuration, i.e. without having to write further code, it enables your java database client
application to make use of features like Fast Connection Failover, Runtime Connection Load-
Balancing and Connection Affinity.
If you are facing this kind of environment, UCP is for you.
A second reason to deal with UCP may be that you have been using ICC, Oracles Implicit
Connection Caching technology, in the past. ICC is deprecated in 11g so you are really well
advised to switch over to UCP. It gives you all ICC could do and a lot more.

4 INTRODUCTION
What you are about to read here is a compilation of procedures and findings concerning the
topic of UCP on Tomcat 7 resulting from a recent BPM software assessment we conducted
here at MT.
While the BPM software itself was not even certified yet for Tomcat 7 and Oracle 11g, we
still figured that this will be our preferred productive setup in a not to distant future. So why
not just go for it?
We had a minor issue with UCP working in our specific environment: The connection pool
was not instantiated with configured number of upfront connections.
Our work around consisted of writing our own custom resource factory for Tomcat. This
work around will be described in detail in this paper.
We are going to discuss some general data pooling topics before going into the details of
setting up a UCP data source and testing it with a most simple test servlet.
We aim for the test servlet to connect with Oracle, borrow a first connection and hope for
UCP to fill up the data source with additional connections according to our data source
specifications (and we really want to see those connections in SQL Developer and jConsole
).

USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 3
5 SOFTWARE VERSIONS
Here are the software versions being:
Tomcat 7.0.16
Oracle 11g Express Edition Release 11.2.0.2.0 – Production
JDK 1.6.0_11
JDBC ojdbc6 release 11.2.0.1.0, UCP for Oracle 11.2.0.x
OS Windows XP Professional SP3
IDE Eclipse Helios JEE Bundle

6 STANDARD TOMCAT CONNECTION POOLING
If you don’t do anything special within Tomcat while defining your data source, which means
you’re using Tomcats standard resource factory for data sources, you’ll still end up with a
pooled data source. Tomcat ships with database connection pooling implemented by the
Apache Commons DBCP project.
I’m not going to match UCP against DBCP here. Right now, I really don’t care which performs
better under what circumstances and the like.
It’s just that I know I’m going to work against an Oracle 11g database, using an Oracle JDBC
implementation and for an Oracle aficionado like me, it is therefore practically imperative to
also use the newest Oracle pooling technology available.

7 CONNECTION POOLING WITH ORACLE
7.1 PREVIOUS ARCHITECTURES
The Implicit Connection Cache was Oracle’s connection pooling architecture up to Oracle 11g
Release 1.
Only with Release 2 ICC has been replaced by UCP so that ICC is now deprecated Oracle 11g
R2 databases.
Switching from ICC to UCP is painless from a functional point of view. All that could be done
with ICC can now be done with UCP.

7.2 UNIVERSAL CONNECTION POOL
The Universal Connection Pool is now the recommended architecture for Java 1.6 clients
connecting to Oracle 11g databases.
UCP is designed to work with single Oracle instance as well as with a whole Oracle Real
Application Cluster.
UCP is the most recent technology for managing pooled connections and is what this paper
focuses on.

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7.3 ORACLE’S RESIDENT CONNECTION POOL
One thing I’d like to mention here is that you can benefit from Oracle’s connection pooling
even if your application cannot for some reason use one of Oracle’s pool-supporting
database drivers (OCI, OCCI, JDBC, ODP.NET etc.).
Oracle supplies the so called “Database Resident Connection Pool” DRCP, a connection pool
managed directly within the database itself.
This connection pool has to be set up by your database administrators via some PLSQL API.
You can configure the pool like this (which is optional and only needed, if you have to
change the default settings):
SQL>execute dbms_connection_pool.configure_pool(null,
minsize=>10,
maxsize=>100,
inactivity_timeout=>300,
max_think_time=>600,
…);

This pool has to be started, before clients can borrow and return connections:
SQL> execute dbms_connection_pool.start_pool;

From the application side, usage of this pool is specified within your SqlNet TNS-Names
connect string.
Hers is an example:
. . .
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp) (HOST=myhost.dom.com)
(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=sales)
(SERVER=POOLED)))
. . .

Oracle 11g supplies a special view to get information from this database resident pool:
dba_cpool_info
Selecting from this view will give you the following info (and more):
select * from dba_cpool_info


Figure 1: Selecting from DBA_CPOOL_INFO

You can see that in my database this pool is inactive (you have to start it like described
above).
The Database Resident Connection Pool is a feature available since Oracle 11g.
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8 SETTING UP UCP
When we were trying to configure UCP data sources on Tomcat 7, we naturally Googled the
topic and of course found a couple of examples demonstrating different configurations.
We had a standard procedure of evaluating a configuration:
• Define the data source in Tomcat
• Add the configuration to our test servlet
• Connect to the database
• Monitor the pool and check for the connections created
The common denominator with all tested configuration was that everything worked fine,
except for the initial creation of the connection pool. The pool was simply not initialized with
configured number of connections on first connect.
Our final solution was to write our own custom resource factory for Tomcat, which was quite
easy to do and gave as absolutely reliable results. We will describe this process here too.

8.1 PREQUISITES
Oracle delivers UCP in a separate file, so you have to download two files:
• Odbc6.jar
• Ucp.jar
Remember, you have to work with Java 1.6 or above to use this JDBC version.
Copy both files into Tomcat’s lib directory: <TOMCAT_HOME>\lib.

8.2 DATASOURCE CONFIGURATION
With Tomcat, data source configurations can be specified either globally, i.e. accessible for
all deployed applications, or on a per application basis.
Global resources are specified in <TOMCAT_HOME>\conf\server.xml whereas application
specific resources are defined in the application’s context.xml file.
Either way the resource is defined in a <Context> element.
In this paper we go for an application specific data source, so the configuration goes into a
separate Context.xml file.
<?xml version="1.0" encoding="UTF-8"?>
<Context override="true">
<Resource name="jdbc/cust_ucp"
auth="Container"
factory="com.mtag.oraclefactory.MtOracleUcpFactory"
type="oracle.ucp.jdbc.PoolDataSource"
connectionFactoryClassName=
"oracle.jdbc.pool.OracleDataSource"
minPoolSize="2"
maxPoolSize="20"
initialPoolSize="5"
user="vk"
password="vk"
url="jdbc:oracle:thin:@localhost:1521:xe"
connectionPoolName="LocalUCP" />
</Context>
USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 6
The factory property needs further explanation which will follow soon.
Everything else is quite straight forward:
• name: the jndi name of the data source
once your application has successfully acquired an Initial Context, you will use this
name to look up the data source
(Tomcat <Resource> attribute)
• auth: Container or Application
let the Container sign on to the resource manager
(Tomcat <Resource> attribute)
• type: fully qualified java class name
represents the object that will be returned by the resource factory, i.e. the JNDI look-
up
(Tomcat <Resource> attribute)
• ConnectionFactoryClassName
property and value taken from UCP manual
• minPoolSize: pool size won’t drop below this value
property taken from UCP manual
• maxPoolSize: pool size won’t grow larger than this
property taken from UCP manual
• user: Oracle user name
property taken from UCP manual
• password: Oracle password for the user above
property taken from UCP manual
• url: Oracle connect string
property taken from UCP manual
• connectionPoolName: the name for this pool
property taken from UCP manual
The attributes “name”, “auth” and “type” are properties from Tomcat’s <Resource>
element.
The rest are UCP properties taken from the UCP manual, which describes how to create and
configure a UCP data source. Please note that these are just the basic ones. There a whole
bunch left for you to integrate into your configuration to make these data sources do what
you require.
The UCP manual is listed in the Further Readings section.

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8.3 PLACING OF CONTEXT.XML
If you go for an application specific context.xml file, you again have two options: you can
place it into your application’s META-INF directory under the name of “context.xml” or
you can copy it into
$CATALINA_BASE/conf/[enginename]/[hostname]/[webappname].xml

Take a note to rename context.xml into [webappname].xml if you go for the second
option. Also be careful to realize that this context descriptor task precedence over anything
you specify in an application specific context descriptor subsequently.
Personally I like my context descriptors application specific. I will copy the context.xml
file into the META-INF directory of my test servlet later on.

8.4 TOMCAT RESOURCE FACTORIES
8.4.1 USING A STANDARD RESOURCE FACTORY
My favorite resource concerning Oracle UCP data pools with Apache Tomcat is Michael
Pilone’s article on the subject listed here: http://drdobbs.com/java/222700353
.
Modifying his data source configuration to suite our environment looks like this:
<Resource name="jdbc/std_pool"

auth="Container"

factory="oracle.ucp.jdbc.PoolDataSourceImpl"

type="oracle.ucp.jdbc.PoolDataSource"

description="UCP Test Data Source"

connectionFactoryClassName="oracle.jdbc.pool.OracleDataSource"

minPoolSize="2"

maxPoolSize="20"
initialPoolSize=”5”

user="vk"

password="vk"

url="jdbc:oracle:thin:@localhost:1521:xe”
connectionPoolName="UcpStdPool"

/>

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Using the above configuration, we get this result when connecting to Oracle:
Figure 2: Connection via Standard Connection Factory

Problem here is, the pool is not created with the correct number of connection as specified
in the “initialPoolSize” parameter.

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A look into jConsole seems to support this:
Figure 3: jConsole inspecting initialPoolSize Parameter

Much to one’s surprise, all other configurations were accepted, as the next figure shows:
Figure 4: Inspected Pool Properties

This is a minor problem which you will probably never notice.
But if it bothers you, one work-around is to program your own custom resource factory.
We will do this in the next section.
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8.4.2 WRITING A CUSTOM RESOURCE FACTORY
Writing a Custom Resource Factory for Tomcat is described within the Tomcat
documentation: http://tomcat.apache.org/tomcat-7.0-doc/jndi-resources-howto.html
. At
the end of this document, you’ll find the chapter “Adding Custom Resource Factories”. Using
this as a guide, we’ll do the following:
• Create a Java project in Eclipse
• Reference all the jars from <TOMCAT_HOME>\lib
• Create a new class that implements javax.naming.spi.ObjectFactory

package com.mtag.oraclefactory;

import java.util.Enumeration;
import java.util.Hashtable;
import java.util.logging.Logger;

import javax.naming.Context;
import javax.naming.Name;
import javax.naming.RefAddr;
import javax.naming.Reference;
import javax.naming.spi.ObjectFactory;

import oracle.ucp.jdbc.PoolDataSource;
import oracle.ucp.jdbc.PoolDataSourceFactory;

/**
* Properties, die diese UCP-Datasource versteht
* o connectionFactoryClassname
* o url
* o user
* o password
* o connectionPoolName
* o minPoolSize
* o maxPoolSize
* o initialPoolSize
*
* @author vkoster
*
*/
public class MtOracleUcpFactory implements ObjectFactory {
private static Logger log =
Logger.getLogger("com.mtag.oraclefactory.MtOracleUcpFactory");
private PoolDataSource pds;

@Override
public Object getObjectInstance(Object obj, Name name, Context nameCtx,
Hashtable<?, ?> environment) throws
Exception {

log.info("MtOracleFactory.getObjectInstance aufgerufen");
pds = PoolDataSourceFactory.getPoolDataSource();
log.info("UCP PooldDataSource besorgt");

USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 11
Reference ref = (Reference)obj;
Enumeration<RefAddr> addrs = ref.getAll();
while (addrs.hasMoreElements()){
RefAddr addr = (RefAddr)addrs.nextElement();
String propName = addr.getType();
String propValue = (String)addr.getContent();
if (propName.toLowerCase().equals("connectionfactoryclassname")) {
pds.setConnectionFactoryClassName(propValue);
} else if (propName.toLowerCase().equals("url")) {
pds.setURL(propValue);
} else if (propName.toLowerCase().equals("user")) {
pds.setUser(propValue);
} else if (propName.toLowerCase().equals("password")) {
pds.setPassword(propValue);
} else if (propName.toLowerCase().equals("connectionpoolname")) {
pds.setConnectionPoolName(propValue);
} else if (propName.toLowerCase().equals("minpoolsize")) {
pds.setMinPoolSize(Integer.parseInt(propValue));
} else if (propName.toLowerCase().equals("maxpoolsize")) {
pds.setMaxPoolSize(Integer.parseInt(propValue));
} else if (propName.toLowerCase().equals("initialpoolsize")) {
pds.setInitialPoolSize(Integer.parseInt(propValue));
}
}
log.info("UCP PooledDataSource konfiguriert und zurückgeliefert");
return pds;
}
}

There is only one method we have to implement: getObjectInstance. Tomcat calls this
method with a lot of parameters, but we are only interested the first one. Formally typed as
an Object, Tomcat passes a javax.naming.Reference object.
From this Reference we can extract a list of name-value pairs, where each pair represents a
data source property that we specified in our Tomcat Conext.xml file.
The implementation does nothing more than to match the name-part of a given name-value
pair with a list of properties I’m interested in and sets the respective property to the value-
part of the pair.
You can do this in a much more flexible manner using reflection, but for demonstration
purposes this hard-coded matching will do.
At the end we simply return the now configured data source.
Finally, export your custom resource factory to a jar-file and copy this into Tomcat’s lib
directory <TOMCAT_HOME>\lib.

9 WRITING A TEST SERVLET
9.1 WHAT THE SERVLET DOES
I wrote a very simple web-app to test different data source configurations.
A static web page invites you to click on a specific data source to be established, one of them
being our UCP connection pool.
USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 12
On clicking one of them, the servlet is invoked doing the following:
• Looking up the respective data source
• borrow a connection
• select and display some information from Oracle’s gv$session table
• close, i.e. return the connection
• maintain a protocol of what happened and display the results
Here are the screenshots:
Figure 5: Static HTML offering different data sources

This page offers a couple of connections to try out. We are interested in the “Custom UCP
Source” connect.
Clicking the link invokes the servlet with the selected data source as a parameter.
Within the servlet, we look up the data source, borrow a connection and query some rows
from the database.
We collect the results along the way and write them to the servlet’s response.

9.2 REFERENCING THE DATA SOURCE IN WEB.XML
Make the use of your data source visible by placing a reference into your applications
web.xml file located in the WEB-INF directory.
My reference looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
USP with Tomcat 7 and Oracle 11g by Volker Koster, MT AG Seite 13
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID"
version="3.0">
<display-name>DataPool</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
<resource-env-ref>
<description>
Referenz auf die Beschreibung der JNDI-Resource im
Context-Element Web-App
</description>
<resource-env-ref-name>
jdbc/oralocal
</resource-env-ref-name>
<resource-env-ref-type>
oracle.jdbc.pool.OracleDataSource
</resource-env-ref-type>
</resource-env-ref>
</web-app>

As you can see from the <display-name> element, my test servlet will be called
“DataPool”.
The data source is referenced by a <resource-enf-ref> element which can be used
here instead of a <resource-ref> element because authentication is already specified in
the context.xml file.
Please take a note that this entry is for documentation purposes only, because we specified
everything in our context.xml file already (this is described in Tomcat’s documentation
within the JNDI Resources HOW-TO,
http://tomcat.apache.org/tomcat-7.0-doc/jndi-
resources-howto.html
in the “context.xml configuration” part).

9.3 BORROWING A CONNECTION
Borrowing a connection from the pool works just like you would expect with any data
source. Here’s the code:
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.DataSource;

public class Connect {
String protocol ="<h2>Trying to connect to Oracle</h2><br>";

public String connectToPool(String dsn){
// Obtain our environment naming context
try {
Context initCtx = new InitialContext();
protocol = protocol + "Initial Context: created<br>";
Context envCtx = (Context) initCtx.lookup("java:comp/env");
protocol = protocol + "Context: java:comp/env<br>";
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//
// Look up our data source
DataSource ds = (DataSource)envCtx.lookup(dsn);
protocol = protocol + "Datasource: "+dsn + "<br>";
//
// Allocate and use a connection from the pool
Connection conn = ds.getConnection();
protocol = protocol + "Connection: borrowed ok<br>";

// query the database
Statement stmt = conn.createStatement();
ResultSet rset = stmt.executeQuery("select sid, username, status,
program from gv$session where upper(username)='VK'");
protocol = protocol+"select sid, username, status, program from
gv$session where username ='VK'<br>";
while (rset.next()) {
protocol = protocol+rset.getString(1)+" "+
rset.getString(2)+" "+
rset.getString(3)+" "+
rset.getString(4)+" "+"<br>";
}

// close everything...
rset.close();
protocol = protocol + "ResultSet closed<br>";
stmt.close();
protocol = protocol + "Statement closed<br>";
conn.close();
protocol = protocol + "Connection: closed<br>";
protocol = protocol + "Connection handling finished OK!<br>";

} catch (Exception e) {
System.out.println(e);
}
return protocol;
}



}

Tomcat ensures that the getObjectInstance-method is called only once for your application.
After this initial call, the object reference is stored in the JNDI-context of your application for
subsequent use.

9.4 VERIFYING THE RESULTS
Now we want to make sure that things are running according to our expectations.
My context.xml file reveals my connection details. You can see that the data source will be
created as user “VK” and password “VK”.
I’m using this account to connect to my SqlDeveloper to Oracle.
Next I query all the sessions of this user from gv$session.
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I expect there to be exactly on session as of now (namely my current SqlDeveloper Session):
Figure 6: Preliminary Actions

Next I point my browser to the location of my test WebApp: http://localhost:8080/DataPool
and click for the UCP data source.

This is the result:
Figure 7: Borrowing a Connection
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The servlet reflects the steps of borrowing a connection. This connection is then used to
retrieve all session of user “VK” from the database.
You can see that we now have 5 JDBC sessions for user VK. This corresponds to the initial
pool size we specified in our context.xml file. Notice that all are marked as INACTIVE except
the one that is actually running this query.
After running the query, the servlet closed the connection, i.e gave it back to pool.
We will now run the same query from SqlDeveloper expecting the connection pool to be still
running.

Figure 8: State of Connection Pool after Closing the Connection

The Connection Pool remains intact but now, all JDBC Connections are INACTIVE.
The SqlDeveloper session is the only one ACTIV, running this query.
On the console running Tomcat, we can see that our custom resource factory was used to
create the UCP data pool:

Figure 9: Tomcat Console

We put some logging into our custom resource factory so you can now trace back the way
our code was called by Tomcat.

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Let’s finally take a look at jConsole to see the UCP classes in action:

Figure 10: Oracles UCP MBean

A drill down into Oracles UCP MBean confirms that the pool has been established according
to our specifications.

10 CONCLUSION
In this paper we demonstrated a way to connect a test servlet running on Tomcat 7 to an
Oracle 11g Database using Oracles Universal Connection Pool Architecture.
We did this to enable further clients to profit from running in clustered Oracle environments.
For some reason not yet clear, we could not take the easy way and accomplish this just by
means of configuration. Instead we had to use a workaround, implementing our own custom
resource factory to get the job done.
Using the work around, UCP worked fine and we could make sure that got what we aimed
for.
We would very much appreciate any feedback as to why this workaround was needed by the
way.

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11 ACKNOWLEDGMENTS
Thanks to my colleges at MT for reviewing my scribbling and making this readable.
Thanks to Peter Rossbach for shedding some light on custom resource factories.

12 READINGS
• Apache Tomcat 7 documentation:
http://tomcat.apache.org/tomcat-7.0-
doc/index.html

• Oracle Database JDBC Developer's Guide and Reference, 11g Release 1 (11.1)
• Oracle Universal Connection Pool for JDBC Developer’s Guide
• Oracle Database JDBC Developer’s Guide and Reference
• http://martincarstenbach.wordpress.com/2011/02/03/getting-up-and-running-with-
universal-connection-pool/

• JDBC Fast Connection Failover with Oracle RAC
Configuring and testing with Tomcat and the Spring framework
By Michael Pilone
February 08, 2010
URL:http://drdobbs.com/java/222700353


13 ABOUT THE AUTOR
Volker Koster is an Executive Architect at MT AG, Ratingen, Germany.
He’s been on software projects since 1990, mostly in Oracle and Java environments.
You can contact him by eMail at volker.koster@mt-ag.com

Your comments are very welcome.



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Balcke-Dürr-Allee 9
40882 Ratingen
Tel. +49 (0) 21 02 309 61-0
Fax +49 (0) 21 02 309 61-10
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