What is a 2 tier connection?
Well, In general, the user system interface client invokes services from the database management server. In many two tier designs, most of the application portion of processing is in the client environment.
The database management server usually provides the portion of the processing related to accessing data (often implemented in store procedures). Clients commonly communicate with the server through SQL statements or a call-level interface.
It should be noted that connectivity between tiers can be dynamically changed depending upon the user’s request for data and services.
Webopedia states “Refers to client/server architectures in which the user interface runs on the client and the database is stored on the server. The actual application logic can run on either the client or the server.”
One of the disadvantages of a two tier setup is performance.
For instance, suppose you get a sudden flood of requests coming in. Your web server might be able to handle the number of incoming connections, but now, since all of the non-DB processing is happening on the same machine, you become CPU-bound, so that, even though the web server can accept more connections, it can’t get enough of the CPU to service all of the requests it has.