oracle数据库设置sid,Oracle数据库系统中实例名（即是SID）和ORACLE_SID的区别

首先介绍几个关于Oracle的基本概念：instance、SID和ORACLE_SID。

instance(Oracle官方给出的定义)

Every running Oracle database is associated with

an Oracle instance. When a database is started on a database server

(regardless of the type of computer), Oracle allocates a memory

area called the System Global Area

(SGA) and starts an Oracle process. This

combination of the SGA and an Oracle process is called an instance.

The memory and the process of an instance manage the associated

database's data efficiently and serve the one or more users of the

database.

system identifier (SID)(同样是Oracle官方给出的定义)

A unique name for an

Oracleinstance.(前面的一句是重点，后面的以我们现在讨论的话题没有直接的关系)

To switch between Oracle

databases, users must specify the desired SID. The SID is included

in theCONNECT DATA

ORACLE_SID (同样是Oracle官方给出的定义)