In my current project I need to connect to a DB2 database on an AS400. To do so is no rocket science, but not exactly a NNF (Next-Next-Finish) config.

First you need to download the IBM JDBC adapter for DB2, which is open souce. Download the JT400.jar  from http://jt400.sourceforge.net/. Place it in a folder on your server. Since it's not an Oracle driver, I don't like to have it placed in the Oracle-Home, so I would put it on a different lib folder, where it is recognisable. Create a logical one, where you place other shared libs as well.

There are several methods to add the lib to your weblogic class path. What worked for me was to add it to the 'setDomainEnv.cmd'/'setDomainEnv.sh' file in the domain home.

(The Default Domain of the integrated weblogic of JDeveloper 12.1.3 under Windows can be found in: “c:\Users\%USER%\AppData\Roaming\JDeveloper\system12.1.3.0.41.140521.1008\DefaultDomain”)
Search for the keyword ‘POST_CLASSPATH’ and add the following at the end of the list of POST_CLASSPATH-additions:

set POST_CLASSPATH=c:\Oracle\lib\jtopen_8_3\lib\jt400.jar;%POST_CLASSPATH%

Where 'c:\Oracle\lib\jtopen_8_3' was the folder where I put it under windows. Then restart your server(s), and create a DataSource. For 'Database Type' as well as for 'Driver' choose 'Other' in the wizard. Then for the following fields enter the corresponding values in the given format (see also the doc.):

Field	Value/Format
URL	jdbc:as400://hostname/Schema-Name;translate binary=true
Driver Class	com.ibm.as400.access.AS400JDBCDriver or com.ibm.as400.access.AS400JDBCXADataSource
Driver Jar	jt400.jar or jt400Native.jar

Since in our case the database apparently has a time out (don't know it this is default behaviour with DB2-AS400), I put in a one-row-query in the Test Table Name-field. And I checked the Test Connections On Reserve-checkbox, because I don't know the time-out frequency.

A description of configuring the library and connection in JDeveloper and the DBAdapter can be found in section 9.6.2 of this doc.

Having the DataSource in Weblogic setup, you can register it in de Database Adapter. Besides provinding the DataSourceName or XADataSourceName you should adapt the PlatformClassName:

The default is 'org.eclipse.persistence.platform.database.oracle.Oracle10Platform' (It only now strikes me that it contains 'org.eclipse.persistence' in the package name). Leaving it like this could have you running in the exception:

ConnectionFactory property platformClassName was set to org.eclipse.persistence.platform.database.oracle.Oracle10Platform but the database you are connecting to is DB2 UDB for AS/400

For DB2 on AS/400, the value should be: 'oracle.tip.adapter.db.toplinkext.DB2AS400Platform', see the docs here.