Mainframe vs. Client/Server

In a client/server architecture, multiple computers typically cooperate to do the same task. For example, in Figure 1.1 the application uses a Web server, a database server, and an LDAP server.

Figure 1.1 Client/server architecture

On a mainframe, the same computer does everything. One security package (RACF, in most cases) protects one operating system kernel. Mainframe subsystems do everything else, as you can see in Figure 1.2.

Figure 1.2 Mainframe architecture

That's a little of the "why" of mainframes. Now let's get started with the "how."