Async Concat Showplan Operator
The Asnyc Concat operator is used only in remote queries (distributed queries). It has n children and one parent node. Usually, some of the children are remote computers that participate in a distributed query. Asnyc Concat issues
open() calls to all of the children simultaneously and then applies a bitmap to each child. For each bit that is a 1, Async Concat sends the output rows to the parent node on demand.