In the cases where you want to use your own Customization Class, make sure that this java class is available to jdeveloper when it restarts. Otherwise , when you use the "Customization Developer" role, you will see that in the Jdeveloper you will see messages like
MDS-00035: cannot load the class:xxxxx

and the customization context will be "none".

To prevent this one way is to create a jar file containing your Customization class and place it in
jdeveloper/jdev/lib/patches.
All the jar files placed in this directory are avaliable in the CLASSPATH when jdev restarts.

While installing soa suite, you might get an error saying that it failed some checks and one of them might be "Zero Swap space while the recommended one is 512MB".

One windows if you get this error then just follow the steps below to set the virtual memory space and restart the machine and try to re install SOA suite.

1) Right click My Compter.
2) Select "Properties" from the context menu.
3) Select Advanced Settings
4) In the dialog that shows up select the "Settings" button in the "Performance" section
5) In the new dialog select "Advanced"
6) In the "Virtual Memory" section click the "Change" button.
7) Now deselect "Automatically manage paging file size for all drivers"
8) Now select "Custom size" and provide "Initial size" of 2 GB and Maximum size of "4 GB".
9) Click "Ok" in all the windows ..

Now restart the machine and try re-installing the soa suite.

XA requirements: The database adapter participates in distributed transactions and requires the back-end database setup for XA recovery by Oracle WebLogic Transaction Manager. Ensure that XA pre-requisites are met. For this, log on to SQL*Plus as a system user, for example, enter sqlplus "/ as sysdba" and then grant the following privileges:
Sql>Grant select on sys.dba_pending_transactions to public.
Sql>Grant execute on sys.dbms_xa to public.
Sql>Grant force any transaction to public;

In many cases you might have to pull data from different databases to show appropriate information in the UI. The crudest way is to use JDBC to fetch data from all the different databases.

If you want to ADFbc then you can have multiple AM's pointing to different databases. But if you want to use the datacontrols properly inside a taskflow (actually any page fragment as well), then you definitely have to understand the how ADFc layer creates the AM instances.

The following blog definitely helps you regarding all the information you need regarding taskflows and the how ADFbc goes hand in hand.

http://one-size-doesnt-fit-all.blogspot.com/2011/05/jdev-11g-task-flows-adf-bc-one-root.html