This read-only Integer32 object reports the maximum number of unacknowledged command messages the VSI master will send to a slave before it must wait for a response, with a value of zero meaning flow control is disabled entirely for that session. An administrator checks this to understand the command throughput and back-pressure behavior of a given VSI session. For example, a session reporting a window size of zero has no flow-control ceiling, so the master can flood commands to that slave without waiting for acknowledgments.