说明：
9I后就不需要重建控制文件了，MAXDATAFILES会自动扩展
只要db_files够，每当超过maxdatafiles，maxdatafiles会翻倍增加。 ---已经确认。
/
1、查看参数
$sqlplus /nolog
conn / as sysdba
SQL> show parameter db_files;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_files integer 200
2、修改参数
SQL> alter system set db_files=800 scope=spfile;
System altered.
3、重启数据库
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 268435456 bytes
Fixed Size 1218892 bytes
Variable Size 75499188 bytes
Database Buffers 188743680 bytes
Redo Buffers 2973696 bytes
Database mounted.
Database opened.
SQL>show parameter db_files
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_files integer 8000
SQL> exit