question about process performance

 now our customer have two question.

1. they have application is like that :

4 app server  -> 1 db server,

they said the app server is all linux, they all select the same table , the sql is same ,

but seem  that in the one of 4 app server is that the same sql run is slowly then in others app server,

they want to kow if is oracle db performance , or just is app server performance？

2.they use top command to monitor processer.

16866 oracle    16   0  5592 1244  868 R    0  0.0   0:00.07 top   -- seem that just in a lot of process ,just one process is running . the others is

                                                                                                                sleep.