SELECT * FROM GLOBAL_NAME;

 show parameter global_name

CREATE DATABASE LINK数据库链接名
    CONNECT TO 用户名 
    IDENTIFIED BY 密码 
    USING ‘数据库连接字符串';

 CREATE PUBLIC DATABASE LINK CONN_MY_LINK
    CONNECT TO MYUSER IDENTIFIED BY MYPASSWORD
    USING 'MYORAL';

  CREATE PUBLIC DATABASE LINK LINK_HSMIS
        CONNECT TO BI 
        IDENTIFIED BY BI 
       USING '(DESCRIPTION =
             (ADDRESS_LIST =
             (ADDRESS = (PROTOCOL = TCP)(HOST = 10.188.245.201)(PORT = 1521))
             )
            (CONNECT_DATA =
            (SERVICE_NAME = hsmis)
            )
        )';

// 赋予创建权限
    grant CREATE DATABASE LINK to smis;    
    grant CREATE SYNONYM to smis;

 SELECT * FROM DUAL@数据库链接名
   或SELECT * FROM表名@数据库链接名

 drop public database link CONN_MY_LINK

 CREATE SYNONYM S_MY_TABLE FOR TABLENAME@数据库链接名;

A_TO_B =  
   (DESCRIPTION =  
   (ADDRESS_LIST =  
   (ADDRESS = (PROTOCOL = TCP)(HOST =A2服务器的IP)(PORT = 1521)) )     
   (CONNECT_DATA =  
   (SERVICE_NAME = B数据库的服务名))) 

 select sess.sid,  
   sess.serial#,  
   lo.oracle_username,  
   lo.os_user_name,  
   ao.object_name,  
   lo.locked_mode  
   from v$locked_object lo,  
   dba_objects ao,  
   v$session sess  
   where ao.object_id = lo.object_id and lo.session_id = sess.sid;

 select * from v$session t1, v$locked_object t2 
   where t1.sid = t2.SESSION_ID;

   alter system kill session 'SID,serial';