Listener refused the connection with the following error: ORA-12519, TNS:no appr

异常:
Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: localhost:1521:orcl 
Hibernate operation: Cannot open connection; uncategorized SQLException for SQL [???]; SQL state [null]; error code [0]; Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: localhost:1521:orcl ; nested exception is java.sql.SQLException: Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: localhost:1521:orcl 


引用
查询数据库当前进程的连接数:

 select count(*) from v$process;

  查看数据库当前会话的连接数:

  elect count(*) from v$session;

  查看数据库的并发连接数:

  select count(*) from v$session where status='ACTIVE';

  查看当前数据库建立的会话情况:

  select sid,serial#,username,program,machine,status from v$session;

  查询数据库允许的最大连接数:

  select value from v$parameter where name = 'processes';

  或者:show parameter processes;

  修改数据库允许的最大连接数:

  alter system set processes = 300 scope = spfile;

  (需要重启数据库才能实现连接数的修改)

  重启数据库:

  shutdown immediate;

  startup;

  查看当前有哪些用户正在使用数据:

  select osuser,a.username,cpu_time/executions/1000000's' ,sql_fulltext,machine

  from v$session a,v$sqlarea b

  where a.sql_address = b.address

  order by cpu_time/executions desc;

  备注:UNIX 1个用户session对应一个操作系统process,而Windows体现在线程。

  启动oracle

  su - oracle

  sqlplus system/pwd as sysdba //进入sql

  startup //启动数据库

  lsnrctl start //启动监听

  sqlplus "/as sysdba"

  shutdown immediate;

  startup mount;

  alter database open;

--

web应用连接oracle数据库时,经常在查询数据时发生

Listener refused the connection with the following error: ORA-12519, TNS:no appropriate service handler found The Connection descriptor used by the client was: 127.0.0.1:1521:ORCL

这种错误,网上查了很多,都说是ip地址改变之后的问题,要把tnsnames.ora中的实例配置中改为计算机名,我试过之后问题还是不能解决,今天终于找到问题所在了,是数据库连接数量的问题,12519错误为监听不能提供服务,通常为数据库进程达到上限导致。

      可以先执行下 select count(*) from v$process ,看下现在系统有多少连接数,然后再查询 select value from v$parameter where name = 'processes' ,看下oracle设置中设置了多少连接数,一般一个应用都会使用20个,所以如果你开了几个应用的话(web、pl/sql、……)就会出这个问题了,这时只需要执行下

alter system set processes = 300 scope = spfile;


就可以了,当然300可以根据实际情况设置。

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