数据库连接数少，报the network adapter could not establish the connection details:
数据库装完后，只能用dbvisualiser连接上，用sql语句报错，the network adapter could not establish the connection details:type:java.sql.sqlException，原因是数据库连接数太少
解决：Sqlplus /nolog
Conn system/密码 as sysdba
select count(*) from v$process --当前的连接数
select value from v$parameter where name = 'processes' --数据库允许的最大连接数

修改最大连接数:
alter system set processes = 1000 scope = spfile;
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;