SQL> startup;
ORA-01031: insufficient privileges
SQL> conn / as sysdba
Connected to an idle instance.
SQL> startup mount;?????????? （启动实例，但不打开数据库）
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.

SQL> alter database open;????????? （启动实例后，再改变数据库为打开）

Database altered.

SQL>shutdown immediate????????? 关闭数据库；
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup????????????????? 启动正常了。
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>