Before a player on Optional Assignment to the minors can be traded or Designated for Assignment, he must be recalled from his minor league assignment ("Recalled - Not to Report").
If a player who was "Recalled - Not to Report" is claimed off waivers while on the Designated List and either the waivers are irrevocable (Outright Assignment Waivers) or the player's club elects not to withdraw a revocable waiver request, the player is assigned to the claiming club.
A player acquired off waivers after being "Recalled - Not to Report" who is subsequently optioned to the minors by his new club must remain on Optional Assignment for a minimum of ten days, unless he is recalled to replace a player on his club's MLB Active List (25-man roster) who is placed on an MLB Inactive List (Disabled List, Bereavement List, Paternity List, etc), or the player is recalled as a "26th Man" for a doublheader scheduled at least 48 hours in advance, or the player's minor league season is over, or the player gets traded. However, if a player is traded after being "Recalled - Not to Report" and then is optioned to the minors by his new club within 24 hours after the trade, the player can be recalled (without any restriction) prior to spending ten days on optional assignment to the minors.
A player who is "Recalled - Not to Report" for the purpose of being Designated for Assignment accrues MLB Service Time equal to the number of days he is on the Designated List prior to being traded, released, or sent outright to the minors.