Adding another application server.

Hi Experts,

My company is having 2 system landscape.

DEV & QAS in one and PRD in one server.

in recent years, my company is growing faster.

i.e increasing number of End users and database growth.

and now the task is to add 2 or more application servers.

my doubts about application server are as follows:-

1 *Deploying application server means is tht installation of sap central instance in

new server or installing an Dailog instance ?

2 *How to add new installed application server to the existing land scape ?

3 *how to group up the added application servers in to a group , so that the

user will get connected to sap by tht group of application server?

requesting you to give some inputs on adding new application server and

solution for database growth ?