原文地址：
http://www.linuxidc.com/Linux/2012-09/69632.htm
以SYS用户进入Oracle，
SQL> grant sysdba to username;
grant sysdba to username
*
ERROR at line 1:
ORA-01994: GRANT failed: password file missing or disabled
首先，把初始化参数REMOTE_LOGIN_PASSWORDFILE的值改成EXCLUSIVE
如果还是有问题，可能是缺少密码文件，用orapwd创建密码文件
$ orapwd -h
Usage: orapwd file=<fname> password=<password> entries=<users>
where
file - name of password file (mand),
password - password for SYS (mand),
entries - maximum number of distinct DBA and OPERs (opt),
There are no spaces around the equal-to (=) character.
这个命令很简单，密码文件一般放在$ORACLE_HOME/dbs目录下，命名规则为orapd+SID,
orapwd FILE='/db/oracle/product/10.2.0/db_1/dbs/orapw+SID' PASSWORD=oracle ENTRIES=5 FORCE=y
然后再执行
SQL> grant sysdba to username;
Grant succeeded.
检查
SQL> select * from v$pwfile_users;
USERNAME SYSDB SYSOP
------------------------------ ----- -----
SYS TRUE TRUE
****** TRUE FALSE
SYSDB那一栏是TRUE就对了
然后就可以as sysdba连接了