oracle

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;
 
 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