Hi Rene @renemendes !
Sry for a delay on this one. Here is an example how to use Try/Catch sequence while writing to Database. You have to use Catch Error (Var Ports) in order to get errors from database Writer node. For start I used Try (Variable Ports) but it can work with Data Ports as well. Here is a print screen.
Additionally I have done same using New Database Integration nodes. There you have DB Insert node that offers more possibilities in configuration and more information in data output port. Check these new nodes out as they are planned to be production ready in KNIME summer release 
Workflow is attached. If any question feel free to ask.
2019_03_29_Try_Catch_DB_Writer.knwf (56.0 KB)
Br,
Ivan