linux下连接oracle数据库出错：ORA-12514 cannot...

今天连接数据库时出了错，监听启动正常，/ 下启动数据库也正常，用sys连接时提示出错，

数据库名是oradb,sid是oradb:

$lsnrctl start

提示：成功！

$sqlplus "/ as sysdba"

sql>startup

提示：成功！

sql>conn sys/oracle@oradb as sysdba;

报错：

ORA-12514: TNS:listener could not resolve SERVICE_NAME given in connect

descriptor！

我是这样解决的：以root身份登录，查看/oracle/product/9.2.0.4/network/admin目录

下的

listener.ora和tnsnames.ora两个配置文件的配置是否正确。

$vi tnsnames.ora

oradb =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.101)(PORT = 1521))
    )
    (CONNECT_DATA =
          (SERVICE_NAME = orcl.oradb.localdomain)
    )
  )
修改SERVICE_NAME = orcl.oradb.localdomain为SERVICE_NAME = oradb

保存退出

$vi listener.ora

LISTENER =   
  (DESCRIPTION_LIST =   
    (DESCRIPTION =   
        (ADDRESS_LIST =   
           (ADDRESS =(PROTOCOL=TCP)(HOST=192.168.0.101)(PORT= 1521))   
         )   
         (ADDRESS_LIST =   
           (ADDRESS =(PROTOCOL=IPC)(KEY=EXTPROC))
         )
    )   
  )
SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = /opt/u01/app/oracle/product/9.2.0.4)
      (PROGRAM = extproc)
    )
  )
在SID_LIST_LISTENER 中增加下列内容：
(SID_DESC =
      (GLOBAL_DBNAME = oradb)
      (ORACLE_HOME = /opt/u01/app/oracle/product/9.2.0.4)
      (SID_NAME = oradb)
)

完整的listener.ora的内容是：

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC0))
      )
      (ADDRESS_LIST =
        (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.101)(PORT = 1521))
      )
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = /opt/u01/app/oracle/product/9.2.0.4)
      (PROGRAM = extproc)
    )
    (SID_DESC =
      (GLOBAL_DBNAME = oradb)
      (ORACLE_HOME = /opt/u01/app/oracle/product/9.2.0.4)
      (SID_NAME = oradb)
    )
  )

再以oracle身份登录，启动监听和数据库，连接数据库都正常了。