Oracle数据库名、实例名、数据库域名、数据库服务名、全局数据库名详解(二)
RACLE_SID,即数据库实例名
以上内容主要是来源于网络，具体原帖已经找不到了，转的到处都是，但总之讲的很好，所以也借鉴了过来。下面是我的小补充：
看下监听状态 --lsnrctl
[plain]
Service "elvis" has 2 instance(s).
Instance"elvis", status UNKNOWN, has 1 handler(s) for this service...
Instance"elvis", status READY, has 1 handler(s) for this service...
Service "elvisXDB" has 1 instance(s).
Instance"elvis", status READY, has 1 handler(s) for this service...
The command completed successfully
可以看出服务名已经被系统占据两个，而服务名可以有64个，但系统占据两个，也就是说我们可以手动配置62个服务名
[sql]
alter system set service_names=b;
更改后，相应的tnsname.ora文件里也需要相应的修改。
[plain]
Service "B" has 1 instance(s).
Instance"elvis", status READY, has 1 handler(s) for this service...
Service "a" has 1 instance(s).
Instance"elvis", status UNKNOWN, has 1 handler(s) for this service...
Service "elvis" has 1 instance(s).
Instance"elvis", status READY, has 1 handler(s) for this service...
Service "elvisXDB" has 1 instance(s).
Instance"elvis", status READY, has 1 handler(s) for this service...
The command completed successfully
数据库实例名的修改
[sql]
alter system set instance_name=test2 scope=spfile;
这个是动态参数，所以需要指定spfile，然后重启数据库才能生效。