Hi Dafa13,
Without OneConnect enabled, LTM will open a serverside connection when a new clientside TCP connection has been established. If multiple clients connect over the same clientside TCP connection, those clients will be sent to the same serverside connection even if the persistence info each client presents points to a different pool member. When you enable OneConnect, among other things, LTM will parse each HTTP request to see if a new serverside connection is required to persist the request to a different server regardless of the current serverside connection open.
This is described more completely in the links on the OneConnect wiki page: http://devcentral.f5.com/wiki/default.aspx/AdvDesignConfig/oneconnect.html
Aaron