Oracle 现在已经是四层结构了：
第一层：用户(瘦的，肥的)
第二层：应用服务器
第三层：Business Logic (JAVA BEAN, .......)
第四层：数据库
以前开发的 Oracle Forms, Reports 还可以做 Client/Server 跑，到 6i时， 你必须要用中间层----应用服务器才能跑！
前天，听说 ORACLE 的 Shared Server (Multi-threaded Server) 要过时，或者已经过时！因为所有的用户都必须通过中间件---应用服务器才能TALK TO Database. 而中间件会用连接池来组织 CONNECTION。故ORACLE 无需担心用户太多问题！
系统设计也好，程序开发也好，我觉得值得借鉴 UNIX DESIGN PHILOSOPHY：
[B] A program should do one littlething and do it well, and combining these small utilities should accomplish more complex tasks.[/B]
UNIX核心之一就是 PIPE， combining these small utilities
it's not a matter of which one's better. it's a matter of whether you want a big lump of code that is hard to maintain and upgrade, or a layered approach which is easy to maintain and upgrade. plus, using a n-tier approach, you can leverage app server functionalities. of course, you can opt to write your own code from scratch as well.
