Safe DP operations document 2006 as attached.
The important factors to this question as stated in other respondents comments, are the knowledge and experience of the personnel managing and controlling the evident conditions presented. Their confidence in the assurance and quality of their equipment (whether it is DP1, 2 or 3) and as stated a fully weighted, risked, and ranked, best practise judgmental assessment of the 'combined conditions' presented for job at hand.
Where neither Anchor handling nor supply can be risked, judged nor decided on one factor alone e.g. sea state.
One has to assess, evaluate and determine combined conditions is such situations on a job by job basis.