From FIXwiki

FIX Message RequestForPositionsAck (MsgType=AO)

MsgType	FIX Specification	First introduced	Deprecated
MsgType=AO	PostTrade messages - PositionMaintenance	FIX.4.4

The Request for Positions Ack message is returned by the holder of the position in response to a Request for Positions message. The purpose of the message is to acknowledge that a request has been received and is being processed.

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Notes

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