Target you can't disable.  Source (kind of) is controlled by ddboost option set distributed-segment-processing command.

do you have any idea how can we verify the source deduplication with data domain.

how can we get sure DSP is processed and does it is required to make the client that will use source deduplication as storage node. any ideas about these commands ?

You can check network traffic against the volume you are backing up - it should be smaller.