oracle啓動三步

[oracle@aa ~]$ export $ORACLE_SID=orcl

[oracle@aa ~]$ echo $ORACLE_SID
orcl

[oracle@aa ~]$ rlwrap sqlplus / as sysdba

SQL*Plus: Release 10.2.0.1.0 - Production on Thu Jun 23 17:14:36 2011

Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup nomount                            <----有參數文件pfile或者spfile就能夠，分配內存，只啓動實例，不加載數據庫。啓動了後臺進程，打開跟蹤文件，警告文件
ORACLE instance started.

Total System Global Area  524288000 bytes
Fixed Size                  1220384 bytes
Variable Size             306184416 bytes
Database Buffers          209715200 bytes
Redo Buffers                7168000 bytes

SQL> alter database mount;                      <----根據參數文件中定義的控制文件路徑，讀入內存。只加載數據庫，不打開數據庫。修改靜態參數要重啓數據庫，在這一步改。

Database altered.

SQL> alter database open;                       <-----打開數據庫。這三步等同於startup.

Database altered.