Davies, 35, who can also play at full-back, made 51 appearances for Pompey last season, scoring once.
Vose, 22, has played twice for the Iron since signing from Wrexham in February.
"I like to get forward and get crosses in. I want to push wingers and full-backs back, attacking is a big part of my game," Davies told the club website.
He began his career at Walsall and his previous clubs also include Chester, Shrewsbury, Notts County and Derby.
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Grimsby have signed former Portsmouth midfielder Ben Davies on a two-year contract and Scunthorpe forward Dominic Vose on a season-long loan.