该问题是由于数据库的连接数不够造成

1)当前的连接数

select count(*) from v$process;

2)数据库允许的最大连接数

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

3)修改最大连接数:

alter system set processes = 300 scope = spfile;

4)重启数据库:

shutdown immediate;

startup;

5)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;

ITPub博客

ORA-12519 TNS no appropriate service handler found