Dedicated Server Configuration (133)

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
process.
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.

專有服務
使用者程式和服務程式分隔開 , 服務程式為每個使用者程式建立一個專有連線 , 是1對1的
在專有服務模式下 , 使用者和服務程式透過不同機制連線 :
1. 使用者和服務程式執行在同一機器上 , 程式介面使用作業系統程式間通訊機制
2. 使用者和服務程式執行在不同機器上 , 程式介面在程式見提供通訊連線機制
3. 專有模式下在有些時候是低效的 .

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