Troubleshooting the 404-not found error on 9iOHS

As already posted here and here, you can easily configure the plsql gateway or the dbms_epg to display the oracle errors directly in the browser instead of receiving a http 404 error and searching for the oracle error in the logfiles.

This is a very good solution for development and test environments, but not for any production system due to security implications.

Recently, I wanted to configure an older Oracle Apache (included in the Oracle 9i release of the database).
It uses the older plsql configuration of the wdbsvr.app configuration file.

Here are the instructions on how to configure APEX with that OHS:
http://www.oracle.com/technology/products/database/application_express/howtos/howto_use9ir2ohs.html.

But how do you configure the DAD now to display the error messages directly?

You can use the following syntax for that:

error_style=Gateway
error_style=GatewayDebug
error_style=WebServer

The default is "WebServer".

See the instructions here:

http://download.oracle.com/docs/cd/A97335_02/apps.102/a90099/config.htm#1005872

Regards,
~Dietmar.