启动数据库实例，分为两步：第一步，启动监听；第二步，启动数据库实例。
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一、如何启动数据库实例
?? 1.进入到sqlplus启动实例
[oracle@redhat ~]$ su - oracle???????????????????????????????? --“切换到oracle用户”
Password:
[oracle@redhat ~]$ lsnrctl start?????????????????????????????? --“打开监听”
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 14-OCT-2009 19:06:40
Copyright (c) 1991, 2005, Oracle.? All rights reserved.
Starting /home/oracle/product/10g/bin/tnslsnr: please wait...
TNSLSNR for Linux: Version 10.2.0.1.0 - Production
System parameter file is /home/oracle/product/10g/network/admin/listener.ora
Log messages written to /home/oracle/product/10g/network/log/listener.log
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC2)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=redhat)(PORT=1522)))
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC2)))
STATUS of the LISTENER
------------------------
Alias???????????????????? LISTENER
Version?????????????????? TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date??????????????? 14-OCT-2009 19:06:40
Uptime??????????????????? 0 days 0 hr. 0 min. 0 sec
Trace Level?????????????? off
Security????????????????? ON: Local OS Authentication
SNMP????????????????????? OFF
Listener Parameter File?? /home/oracle/product/10g/network/admin/listener.ora
Listener Log File???????? /home/oracle/product/10g/network/log/listener.log
Listening Endpoints Summary...
? (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC2)))
? (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=redhat)(PORT=1522)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
? Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
[oracle@redhat ~]$ sqlplus /nolog??????????????????????????????? --“进入到sqlplus”
SQL*Plus: Release 10.2.0.1.0 - Production on Wed Oct 14 19:06:45 2009
Copyright (c) 1982, 2005, Oracle.? All rights reserved.
SQL> conn /as sysdba????????????????????????????????????????????? --“连接到sysdba”
Connected to an idle instance.
SQL> startup???????????????????????????????????????????????????? --“启动数据库实例”
ORACLE instance started.
Total System Global Area? 285212672 bytes
Fixed Size????? 1218968 bytes
Variable Size???? 88082024 bytes
Database Buffers?? 188743680 bytes
Redo Buffers????? 7168000 bytes
Database mounted.
Database opened.
SQL> shutdown immediate????????????????????????????????????????? --“关闭数据库实例”
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> exit
Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
[oracle@redhat ~]$ lsnrctl stop???????????????????????????????? --“关闭监听”
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 14-OCT-2009 19:08:06
Copyright (c) 1991, 2005, Oracle.? All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC2)))
The command completed successfully
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?? 2.用dbstart和dbshut启动和关闭数据库实例
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先启动监听 lsnrctl start
启动实例? dbstart
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使用dbstart命令启动数据库比较方便，但是在linux上安装好oracle之后，第一次使用dbstart命令可能会报如下错误：
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ORACLE_HOME_LISTNER is not SET, unable to auto-start Oracle Net Listener
Usage: /u01/app/oracle/oracle/product/10.2.0/db_1/bin/dbstart ORACLE_HOME

原因：
dbstart和dbshut脚本文件中ORACLE_HOME_LISTNER的设置有问题，分别打开两个文件找到：用vi编辑dbstart，ORACLE_HOME_LISTNER=$1,修改为
ORACLE_HOME_LISTNER=$ORACLE_HOME
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然后保存退出，此时再运行dbstart，已经不报错了，但是没有任何反应，ps一下进程，没有oracle的进程，说明oracle实例没有正常启动。
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此时的原因是在/etc/oratab的设置问题，我们vi一下，发现
zgz:/home/oracle/product/10g:N
最后设置的是"N"（我的环境中只有一个实例，因此只有一行配置语句），我们需要把“N”修改为“Y”。
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以上的工作做好之后，dbstart就可以正常使用了：
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[oracle@redhat bin]$ lsnrctl start?????????????????????????????????? --“启动监听”
LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 14-OCT-2009 19:44