ORA-00020: maximum number of processes (40) exceeded模拟会话连接数满
问题描述：在正式生产环境中，有的库建的process和session连接数目设置的较小，导致后期满了无法连接。因为正式库无法进行停库修改，只能释放连接，做个测试模拟
1. 修改现有最大会话与进程连接数
SQL> alter system set processes = 35 scope = spfile; System altered. SQL> alter system set sessions = 40 scope = spfile; System altered.
2.重启生效,加大连接数
通过打开会话框以及连接plsql窗口制造连接数
制造到一定数目时，会发现sqlplus已经登陆不上去
后台日志：
ORA-00020: maximum number of processes (40) exceeded
ORA-20 errors will not be written to the alert log for
the next minute. Please look at trace files to see all
the ORA-20 errors.
此时的连接数情况
SQL> select count(*) from v$process; COUNT(*) ---------- 39 SQL> select count(*) from v$session; COUNT(*) ---------- 36
3.删除无效session
<一> plsql删除会话
选中要删除的会话，删除完后在后台不会直接释放，在连接窗口执行命令会发现会话和已经被killed掉，然后这边后台释放完成
<二> sqlplus删除会话
查询会话
SQL> select username,status,wait_time,last_call_et from v$session; USERNAME STATUS WAIT_TIME LAST_CALL_ET ------------------------------ -------- ---------- ------------ ACTIVE 0 1874 ACTIVE 0 1873 ACTIVE 0 1873 ACTIVE 0 1873 ACTIVE 0 1869 ACTIVE 0 1868 ACTIVE 0 1858 SYS INACTIVE 0 1805 SYS ACTIVE -1 0 ACTIVE 0 1873 ACTIVE 0 1873 USERNAME STATUS WAIT_TIME LAST_CALL_ET ------------------------------ -------- ---------- ------------ ACTIVE 0 1873 ACTIVE 0 1868 SYSTEM INACTIVE 0 1826 ACTIVE 0 1858 SYS INACTIVE 0 1711 SYS INACTIVE 0 826 ACTIVE 0 1874 ACTIVE 0 1873 ACTIVE 0 1873 ACTIVE 0 1873 ACTIVE 0 1868 USERNAME STATUS WAIT_TIME LAST_CALL_ET ------------------------------ -------- ---------- ------------ ACTIVE 0 1868 SYS INACTIVE 0 1809 SYS INACTIVE 0 1705 SYS INACTIVE 0 1633 SYS INACTIVE 0 1417 ACTIVE 0 1874 ACTIVE 0 1873 ACTIVE 0 1873 ACTIVE 0 1873 SYS INACTIVE 0 1813 ACTIVE 0 1868 USERNAME STATUS WAIT_TIME LAST_CALL_ET ------------------------------ -------- ---------- ------------ SYS INACTIVE 0 1757 SCOTT INACTIVE 0 24 SYSTEM INACTIVE 0 1567 36 rows selected.
生成kill会话语句
SQL> select 'alter system kill session '''||sid||','||serial#||''';'from v$session where LAST_CALL_ET>500 AND status='INACTIVE'; 'ALTERSYSTEMKILLSESSION'''||SID||','||SERIAL#||''';' -------------------------------------------------------------------------------- alter system kill session '11,1'; alter system kill session '26,21'; alter system kill session '28,29'; alter system kill session '29,7'; alter system kill session '51,3'; alter system kill session '52,9'; alter system kill session '53,9'; alter system kill session '64,9'; alter system kill session '69,17'; alter system kill session '73,31'; alter system kill session '74,5'; 'ALTERSYSTEMKILLSESSION'''||SID||','||SERIAL#||''';' -------------------------------------------------------------------------------- alter system kill session '75,13'; 12 rows selected.
执行sql语句
SQL> alter system kill session '11,1'; SQL> alter system kill session '26,21'; SQL> alter system kill session '28,29'; SQL> alter system kill session '29,7'; SQL> alter system kill session '51,3'; SQL> alter system kill session '52,9'; SQL> alter system kill session '53,9'; SQL> alter system kill session '64,9'; SQL> alter system kill session '69,17'; SQL> alter system kill session '73,31'; SQL> alter system kill session '74,5';
在后台其中一个连接会话执行命令，已经语法执行
SQL> archive log list;
ORA-00028: your session has been killed
<三> 操作系统kill会话
查询不活跃会话的sid，转换为操作系统的pid，通过操作系统进行kill掉进程
SQL> select username,sid,serial#,status,last_call_et from v$session where status='INACTIVE'; USERNAME SID SERIAL# STATUS LAST_CALL_ET ------------------------------ ---------- ---------- -------- ------------ SYS 11 3 INACTIVE 340 SYS 28 31 INACTIVE 258 SYS 51 5 INACTIVE 267 SYS 52 11 INACTIVE 255 SYS 53 11 INACTIVE 253 SYS 69 19 INACTIVE 261 SCOTT 74 7 INACTIVE 7 SYSTEM 75 13 INACTIVE 3429
sid转换为spid
select spid from v$process where addr in (select paddr from v$session where sid=11); select spid from v$process where addr in (select paddr from v$session where sid=28); select spid from v$process where addr in (select paddr from v$session where sid=51); select spid from v$process where addr in (select paddr from v$session where sid=52); select spid from v$process where addr in (select paddr from v$session where sid=53); select spid from v$process where addr in (select paddr from v$session where sid=69); select spid from v$process where addr in (select paddr from v$session where sid=74); select spid from v$process where addr in (select paddr from v$session where sid=75);
操作系统进程kill掉
[oracle@orcl ~]$ kill -9 5294 [oracle@orcl ~]$ kill -9 5391 [oracle@orcl ~]$ kill -9 5384 -bash: kill: (5384) - No such process [oracle@orcl ~]$ kill -9 5393 [oracle@orcl ~]$ kill -9 5395 [oracle@orcl ~]$ kill -9 5389 [oracle@orcl ~]$ kill -9 5413 [oracle@orcl ~]$ kill -9 4996
查看现有连接，已经被释放
SQL> archive log list;
ORA-03135: connection lost contact
查看连接数据库连接数
SQL> select count(*) from v$session;
COUNT(*)
----------
29
SQL> select count(*) from v$process;
COUNT(*)
----------
35
<四> ALTER SYSTEM DISCONNECT SESSION
POST_TRANSACTION表示等待事务完成后断开会话，IMMEDIATE表示中断会话，立即回滚事务。使用immediate可以立即释放会话
SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' POST_TRANSACTION;
SQL> ALTER SYSTEM DISCONNECT SESSION 'sid,serial#' IMMEDIATE;
<五> 增加进程和会话数，不过要停库
1.查看processes和sessions参数 show parameter processes show parameter sessions select count(*) from v$session ; --当前的session连接数 select count(*) from v$process ; --当前的数据库连接数 select value from v$parameter where name ='processes'; --数据库允许的最大连接数 2.修改processes和sessions值 alter system set processes=1000 scope=spfile; alter system set sessions=1105 scope=spfile;
3.重启数据库 shutdown immediate; startup;
