The user and server processes are separate, distinct processes. The separate server
process created on behalf of each user process is called a dedicated server process (or
shadow process), because this server process acts only on behalf of the associated user
This configuration maintains a one-to-one ratio between the number of user processes
and server processes. Even when the user is not actively making a database request,
the dedicated server process remains (though it is inactive and can be paged out on
some operating systems).
In the dedicated server configuration, the user and server processes communicate
using different mechanisms:
■ If the system is configured so that the user process and the dedicated server
process run on the same computer, the program interface uses the host operating
system’s interprocess communication mechanism to perform its job.
■ If the user process and the dedicated server process run on different computers,
the program interface provides the communication mechanisms (such as the
network software and Oracle Net Services) between the programs.
■ Dedicated server architecture can sometimes result in inefficiency. Consider an
order entry system with dedicated server processes. A customer places an order as
a clerk enters the order into the database. For most of the transaction, the clerk is
talking to the customer while the server process dedicated to the clerk’s user
process remains idle. The server process is not needed during most of the
transaction, and the system is slower for other clerks entering orders. For
applications such as this, the shared server architecture may be preferable.
用户进程和服务进程分隔开 , 服务进程为每个用户进程创建一个专有连接 , 是1对1的
在专有服务模式下 , 用户和服务进程通过不同机制连接 :
1. 用户和服务进程运行在同一机器上 , 程序接口使用操作系统进程间通信机制
2. 用户和服务进程运行在不同机器上 , 程序接口在程序见提供通信连接机制
3. 专有模式下在有些时候是低效的 .
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