I have heard people saying web is three tier connection in several interview and desktop (with I-server) is a two tier connection. Such answers about tiers really gives me tears. [:)]. You are hear reading this page just mean that you are too lazy to read the MicroStrategy PDFs. Anyways here is the information about various tiers.
Anything that doesn’t requires I-server is 2 tier. One can have two tier connection not only with Access but also SQL Server, Oracle, Netizza, Teradata, etc, In fact with any damn database. In such case, Desktop and Metadata/Database are two tires. DSN is important in this case. In fact that become heart in 2 tier. You never need to use Configuration Manager in case of a 2 tier connection.
Any time you use configuration manager to connect I-Server to Metadata (obviously with DSN) is a three tier. In this case the tiers are, Desktop – I-Server – Metadata/Database.
Any time you use Web is a 4 tier architecture. And tiers are as follows.
Web Browser – Web Server – I-Server – Metadata/Database.
A 5 tier architecture is also possible. There are various vendors who sell installable reporting tool based on MicroStrategy architecture. In this case the 5th tier sits between Web Browser and Server.