How to start Oracle service in UNIX

A. In order to start Oracle service in UNIX you need to login as a Oracle user. 
Use su - command to login as oracle user.
Start Oracle server in UNIX

Type the following command, enter:
$ su - oracle
Now use lsnrctl command to start service (usually located at /home/oracle/oracle/product/10.2.0/db_1/bin directory):
$ lsnrctl start

Next start database:

$ dbstart
Stop Oracle service in UNIX

To stop Oracle servuice type following two commands:
$ lsnrctl stop
$ dbshut

NOTE:  需要注意的是，启动的sid是通过环境变量指定的，这个很重要。 如果想起多个实例，一个就是通过修改环境变量，启动多个。或者是创建多个用户，每个用户有不通的环境变量来启动不同的sid。