CSY Query

Hi,
I have a doubt/Query.
Condition:
There are two clients <"A1" and "A2"> opening the port in sharable mode.
Both clients have their read request
Both uses same CSY.
The data comes from H/W.
Data is received by CSY from H/W
Now, Who decides it, which data to go for "A1" and "A2".
<How is the data send from CSY to A1 and CSY to A2??>

Plz tell me the way or any API if known!!

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