先看有没有sqlnet.ora
[Oracle@localhost ~]$ cd $ORACLE_HOME
[oracle@localhost dbhome_1]$ cd network
[oracle@localhost network]$ cd admin
[oracle@localhost admin]$ ls
listener.ora samples shrept.lst
[oracle@localhost admin]$
VMware+Linux+Oracle 10G RAC全程详细图解
在CentOS 6.4下安装Oracle 11gR2(x64)
手动创建一个sqlnet.ora文件
[oracle@localhost admin]$ touch sqlnet.ora
[oracle@localhost admin]$ vim sqlnet.ora
[oracle@localhost admin]$ cat sqlnet.ora
SQLNET.AUTHENTICATION_SERVICES=(none);
[oracle@localhost admin]$
试验登陆情况：
[oracle@localhost admin]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Apr 15 08:26:25 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-01017: invalid username/password; logon denied
Enter user-name:
*********************************
查看口令文件情况：
[oracle@localhost dbs]$ pwd
/u01/app/oracle/product/11.2.0/dbhome_1/dbs
[oracle@localhost dbs]$ ls
hc_orcl.dat init.ora initorcl.ora lkORCL orapworcl spfileorcl.ora
[oracle@localhost dbs]$
现在执行口令文件处理：
用老的口令文件改口令不被允许：
[oracle@localhost dbs]$ orapwd file=orapworcl password=gaojian
OPW-00005: File with same name exists - please delete or renam
只好再作一个新的：
[oracle@localhost dbs]$ orapwd file=orapwgaojian password=gaojian
[oracle@localhost dbs]$ ls
hc_orcl.dat initorcl.ora orapwgaojian spfileorcl.ora
init.ora lkORCL orapworcl
[oracle@localhost dbs]$
用刚刚作好的口令，还是不行（因为它和oracle中的sys口令不一致，是我随便设的，所以不行，其实登陆到哪个实例，就会用哪个口令文件--orapw<SID>）：
[oracle@localhost admin]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Apr 15 08:32:23 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-01017: invalid username/password; logon denied
Enter user-name: sys as sysdba
Enter password:
ERROR:
ORA-01017: invalid username/password; logon denied
Enter user-name: sys
Enter password:
ERROR:
ORA-01017: invalid username/password; logon denied
SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus
[oracle@localhost admin]$
*******************************
考虑删除orapworcl （这个操作实际上有一定的危险性）:
[oracle@localhost dbs]$ rm orapworcl
[oracle@localhost dbs]$
一样也是登陆不进去：
[oracle@localhost admin]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Apr 15 08:34:24 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
ERROR:
ORA-01017: invalid username/password; logon denied
Enter user-name: sys as sysdba
Enter password:
ERROR:
ORA-01017: invalid username/password; logon denied
Enter user-name: sys
Enter password:
ERROR:
ORA-01017: invalid username/password; logon denied
SP2-0157: unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus
[oracle@localhost admin]$
*******************************
把sqlnet.ora中的 SQLNET.AUTHENTICATION_SERVICES=(none); 注释掉，再试验：
[oracle@localhost admin]$ cat sqlnet.ora
#SQLNET.AUTHENTICATION_SERVICES=(none);
[oracle@localhost admin]$
[oracle@localhost dbs]$ strings orapwgaojian
]\[Z
ORACLE Remote Password file
INTERNAL
FE406C76B620912C
861BAF16E111B672
[oracle@localhost dbs]$
登陆到数据库中，来更改口令：
[oracle@localhost admin]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Tue Apr 15 08:44:08 2014
Copyright (c) 1982, 2013, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> alter user sys identified by oracle;
User altered.