When you set properties using the Set Properties shape they will overwrite the properties that you use in extensions. The extended properties are set at the start of the process.
To test this you could build a simple process that has a No Data Start Shape -> Message Shape, (that shows the properties) -> Set Properties Shape -> Message Shape, (that shows the properties) -> Stop. It would look something like this. Process properties were used for this test, however, the same applies to dynamic process properties.
Remember to have the properties extensible by going into extensions and clicking the check box on the properties.
Process Extensions dialog- http://help.boomi.com/atomsphere/GUID-954599FD-0FE5-4D3D-9A6A-FA68086A290F.html
When you run the test, click on "Test Extensions" which is under the atom you choose to run the test. Click on process properties and choose the property you wish to extend and enter a value for that property. Then click on "Run Test".
After the test completes you will be able to see that the properties that were extended show up for the first message shape but after they are set in the Set Properties shape they are overwritten and are now those values instead of the extended ones. This also happens when you use environment extensions and deploy the process.
Reference Guide Articles
Here are some links to our Reference Guide, which you may find useful when using and configuring [Core Concept].
- Environment Extensions dialog - http://help.boomi.com/atomsphere/GUID-738AC3FD-D903-4C8F-978F-7F89D351AD00.html
- Process extensions - http://help.boomi.com/atomsphere/GUID-D3BC60D9-2839-47E0-8EFE-4664257DDD9D.html
- Process extension values - http://help.boomi.com/atomsphere/GUID-B07B2E1F-0E00-4D62-A67C-826316B2C525.html
- Atom Extensions dialog - http://help.boomi.com/atomsphere/GUID-149A58F4-A6C9-4F67-B406-2FD8D0FD3ADD.html