Do you have a valueChangeListener for the <h:selectonemenu> and <h:Secondselectonemenu> ?
Sounds like a ViewHandler issue: "The pluggablity mechanism for allowing implementations of or applications using the JavaServer Faces specification to provide their own handling of the activities in the Render Response and Restore View phases"
Thus: Datatable should be wrapped with a ViewHandler which should capture changes in the view.
I am not familiar with jsf so this is the best I can do. HTH
"The differential equations that describe dynamic interactions of power generators are similar to that of the gravitational interplay among celestial bodies, which is chaotic in nature."