So, its actually much more in conjunction with arpeggio then "stand alone" hold function. Thanks for the input guys.
Yes, if you just activate hold in normal play mode (without the apreggiator) it will make the notes last forever, depending on the sustain setting of the VCA envelope.
If you activate hold while the arpeggiator is on, it puts the arpeggiator in relatch mode, which means that if you play changing chords on the keyboard, the arpeggio will consist only of the notes of the chord you are currently playing, i.e. each new chord you play will replace the arpeggio from before. BUT: That only works if you don't play legato. As soon as you keep holding down one note during a chord change the new notes will be added to the arpeggio that's already playing.