关于数据库关闭的问题

我先用shutdown normal关闭了数据库，可是它很慢，几十分钟过去了纹丝不动，又打不开，后来用shutdown abort解决的。

C:\>sqlplus/nolog

SQL> conn sys/ as sysdba

输入口令:

已连接到空闲例程。

SQL> startup

ORA-10997: another startup/shutdown operation of this instance inprogress

ORA-09968: unable to lock file

SQL> shutdown immediate

ORA-24324: 未初始化服务句柄

ORA-24323: 不允许此值

ORA-01090: shutdown in progress - connection is not permitted

SQL> startup nomount

ORA-10997: another startup/shutdown operation of this instance inprogress

SQL> startup mount

ORA-10997: another startup/shutdown operation of this instance inprogress

SQL> shutdown abort

ORACLE 例程已经关闭。

SQL> startup

ORACLE 例程已经启动。

Total System Global Area 167772160 bytes

Fixed Size 1247900 bytes

Variable Size 79693156 bytes

Database Buffers 83886080 bytes

Redo Buffers 2945024 bytes

数据库装载完毕。

数据库已经打开。

SQL>