今天一网友咨询数据库宕机了，当时数据库出现用户无法登录的症状，为了了解起因，去查看了网友的告警日志alert.log，发现在晚上10:00左右出现大量的ORA-00020: No more process state objects available 错误，具体错误日志如下:
Fatal NI connect error 12170.
VERSION INFORMATION:
TNS for Linux: Version 11.2.0.2.0 - Production
Oracle Bequeath NT Protocol Adapter for Linux: Version 11.2.0.2.0 - Production
TCP/IP NT Protocol Adapter for Linux: Version 11.2.0.2.0 - Production
Time: 11-MAY-2015 14:28:28
Tracing not turned on.
Tns error struct:
ns main err code: 12535
TNS-12535: TNS:operation timed out
ns secondary err code: 12560
nt main err code: 505
TNS-00505: Operation timed out
nt secondary err code: 110
nt OS err code: 0
Client address: (ADDRESS=(PROTOCOL=tcp)(HOST=192.168.102.150)(PORT=50069))
Mon May 11 16:21:14 2015
Thread 1 cannot allocate new log, sequence 1728
Private strand flush not complete
Current log# 4 seq# 1727 mem# 0: /oradata/orcl/redo4.log
Thread 1 advanced to log sequence 1728 (LGWR switch)
Current log# 3 seq# 1728 mem# 0: /oradata/orcl/redo3.log
Mon May 11 22:00:00 2015
Setting Resource Manager plan SCHEDULER[0x3107]:DEFAULT_MAINTENANCE_PLAN via scheduler window
Setting Resource Manager plan DEFAULT_MAINTENANCE_PLAN via parameter
Mon May 11 22:00:00 2015
Starting background process VKRM
Mon May 11 22:00:00 2015
VKRM started with pid=83, OS id=27195
Tue May 12 00:56:23 2015
Thread 1 cannot allocate new log, sequence 1729
Private strand flush not complete
Current log# 3 seq# 1728 mem# 0: /oradata/orcl/redo3.log
Thread 1 advanced to log sequence 1729 (LGWR switch)
Current log# 1 seq# 1729 mem# 0: /oradata/orcl/redo01.log
Tue May 12 02:00:00 2015
Closing scheduler window
Closing Resource Manager plan via scheduler window
Clearing Resource Manager plan via parameter
Tue May 12 10:46:48 2015
Thread 1 cannot allocate new log, sequence 1730
Private strand flush not complete
Current log# 1 seq# 1729 mem# 0: /oradata/orcl/redo01.log
Thread 1 advanced to log sequence 1730 (LGWR switch)
Current log# 2 seq# 1730 mem# 0: /oradata/orcl/redo2.log
Tue May 12 14:36:13 2015
Thread 1 cannot allocate new log, sequence 1731
Private strand flush not complete
Current log# 2 seq# 1730 mem# 0: /oradata/orcl/redo2.log
Thread 1 advanced to log sequence 1731 (LGWR switch)
Current log# 4 seq# 1731 mem# 0: /oradata/orcl/redo4.log
Tue May 12 16:27:07 2015
Thread 1 cannot allocate new log, sequence 1732
Private strand flush not complete
Current log# 4 seq# 1731 mem# 0: /oradata/orcl/redo4.log
Thread 1 advanced to log sequence 1732 (LGWR switch)
Current log# 3 seq# 1732 mem# 0: /oradata/orcl/redo3.log
Tue May 12 22:00:00 2015
Setting Resource Manager plan SCHEDULER[0x3108]:DEFAULT_MAINTENANCE_PLAN via scheduler window
Setting Resource Manager plan DEFAULT_MAINTENANCE_PLAN via parameter
Tue May 12 22:00:00 2015
Starting background process VKRM
Tue May 12 22:00:00 2015
VKRM started with pid=174, OS id=25804
Wed May 13 02:00:00 2015
Closing scheduler window
Closing Resource Manager plan via scheduler window
Clearing Resource Manager plan via parameter
Wed May 13 02:45:10 2015
Thread 1 cannot allocate new log, sequence 1733
Private strand flush not complete
Current log# 3 seq# 1732 mem# 0: /oradata/orcl/redo3.log
Thread 1 advanced to log sequence 1733 (LGWR switch)
Current log# 1 seq# 1733 mem# 0: /oradata/orcl/redo01.log
Wed May 13 09:05:36 2015
Time drift detected. Please check VKTM trace file for more details.
Wed May 13 09:15:55 2015
DM00 started with pid=352, OS id=4784, job SYSTEM.SYS_EXPORT_SCHEMA_01
Wed May 13 09:15:56 2015
DW00 started with pid=353, OS id=4786, wid=1, job SYSTEM.SYS_EXPORT_SCHEMA_01
Wed May 13 10:11:52 2015
Thread 1 cannot allocate new log, sequence 1734
Private strand flush not complete
Current log# 1 seq# 1733 mem# 0: /oradata/orcl/redo01.log
Thread 1 advanced to log sequence 1734 (LGWR switch)
Current log# 2 seq# 1734 mem# 0: /oradata/orcl/redo2.log
Wed May 13 13:15:38 2015
Thread 1 cannot allocate new log, sequence 1735
Private strand flush not complete
Current log# 2 seq# 1734 mem# 0: /oradata/orcl/redo2.log
Thread 1 advanced to log sequence 1735 (LGWR switch)
Current log# 4 seq# 1735 mem# 0: /oradata/orcl/redo4.log
Wed May 13 14:54:18 2015
Thread 1 cannot allocate new log, sequence 1736
Private strand flush not complete
Current log# 4 seq# 1735 mem# 0: /oradata/orcl/redo4.log
Thread 1 advanced to log sequence 1736 (LGWR switch)
Current log# 3 seq# 1736 mem# 0: /oradata/orcl/redo3.log
Wed May 13 17:39:31 2015
Thread 1 cannot allocate new log, sequence 1737
Private strand flush not complete
Current log# 3 seq# 1736 mem# 0: /oradata/orcl/redo3.log
Thread 1 advanced to log sequence 1737 (LGWR switch)
Current log# 1 seq# 1737 mem# 0: /oradata/orcl/redo01.log
Wed May 13 20:47:10 2015
ORA-00020: No more process state objects available
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.
Process m000 submission failed with error = 20
Wed May 13 20:52:37 2015
ORA-00020: No more process state objects available
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.
Process m000 submission failed with error = 20
Wed May 13 20:57:38 2015
ORA-00020: No more process state objects available
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.
Process m000 submission failed with error = 20
Wed May 13 21:01:35 2015
ORA-00020: No more process state objects available
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.
Process W001 submission failed with error = 20
Wed May 13 21:02:38 2015
ORA-00020: No more process state objects available
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.
Process m001 submission failed with error = 20
Wed May 13 21:05:44 2015
ORA-00020: No more process state objects available
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.
Process W001 submission failed with error = 20
Wed May 13 21:12:38 2015
ORA-00020: No more process state objects available
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.
Process m000 submission failed with error = 20
Process m001 submission failed with error = 20
Wed May 13 21:42:39 2015
ORA-00020: No more process state objects available
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.
Process m000 submission failed with error = 20
Process m001 submission failed with error = 20
Wed May 13 21:43:00 2015
Process W001 submission failed with error = 20
Wed May 13 21:51:13 2015
Adjusting the default value of parameter parallel_max_servers
from 1280 to 385 due to the value of parameter processes (400)
Starting ORACLE instance (normal)
Wed May 13 21:52:40 2015
ORA-00020: No more process state objects available
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.
Process m000 submission failed with error = 20
Wed May 13 21:53:33 2015
错误信息一般在Oracle实例在创建一些辅助后台进程(如mmon的子进程m00x或者子进程W00x等)时出现进程启动失败时出现，而造成该错误的可能性有多种，包括Oracle实例资源不足、操作系统资源不足等等。其中较为常见的是实例instance的process使用达到上限，可以通过查询v$resource_limit视图来了解实例生命周期内是否发生过process总数暴满的情况:
我们可以看到processes的MAX_UTILIZATION最大使用数目曾到过LIMIT_VALUE限定的400，
sessions达到了640.
从以上V$resource_limit视图的输出来看，极有可能是processes总数达到上限导致了新的后台辅助进程创建失败，其实我们可以很方便地验证这一点:
[oracle@bntjftest ~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.4.0 Production on Thu May 14 15:28:15 2015
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