Here is a way you can test & create DBC file from the application.
First of all Login to Oracle application for which you want to generate the DBC file referring below URL
Navigate to end of the page and click on Enter AOL/J Setup Test
On the next screen you can click on Locate DBC File. Here you can see DBC file you can copy these contents and make a DBC file to be used in OAF development by putting it under $JDEV_USER_HOME/dbc_files/secure folder
We can click on Next link to go to Verify setting in DBC file
We can click on next to test our Application login.
Click on Test Application Login.
Similarly, you have several options on left hand side that you can use as shown below.