昨天处理了一个小case，后来发现不知道哪位亲爱的朋友修改了/etc/hosts文件，导致数据库趴下了，记录一下

[root@padb ~]# su - oracle
$
$ps -ef|grep ora_
oracle    5874  5847  0 11:35 pts/3    00:00:00 grep ora_
$lsnrctl status

LSNRCTL for Linux: Version 11.2.0.3.0 - Production on 12-JUL-2018 11:35:33

Copyright (c) 1991, 2011, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost)(PORT=1521)))

###########监听卡在这里了####################

$ps -ef|grep lsnr
oracle    5808  5757  0 11:34 pts/1    00:00:00 lsnrctl start
oracle    5810     1 99 11:34 ?        00:01:36 /u01/app/oracle/product/11.2.0/dbhome_1/bin/tnslsnr LISTENER -inherit
oracle    5877  5847  0 11:35 pts/3    00:00:00 grep lsnr

##############进程在
$kill -9 5810
$ps -ef|grep lsnr
oracle    5879  5847  0 11:35 pts/3    00:00:00 grep lsnr

##############kill 进程 
$sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Thu Jul 12 11:35:56 2018

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected.
SQL> 

###############很诡异的一个状态，竟然connected了

##############查看日志
$uptime
 11:36:27 up 50 min,  4 users,  load average: 0.42, 0.33, 0.47
$adrci

ADRCI: Release 11.2.0.3.0 - Production on Thu Jul 12 11:36:35 2018

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

ADR base = "/u01/app/oracle"
adrci> show alert

Choose the alert log from the following homes to view:

1: diag/clients/user_oracle/host_61728193_80
2: diag/rdbms/padb/padb
3: diag/tnslsnr/localhost/listener
4: diag/tnslsnr/padb/listener
Q: to quit

Please select option: 2
Output the results to file: /tmp/alert_5886_14061_padb_1.ado
2017-12-05 18:40:29.250000 +08:00
Starting ORACLE instance (normal)
****************** Large Pages Information *****************

Total Shared Global Region in Large Pages = 0 KB (0%)

Large Pages used by this instance: 0 (0 KB)
Large Pages unused system wide = 0 (0 KB) (alloc incr 64 MB)
Large Pages configured system wide = 0 (0 KB)
Large Page size = 2048 KB

RECOMMENDATION:
  Total Shared Global Region size is 24 GB. For optimal performance,
  prior to the next instance restart increase the number
  of unused Large Pages by atleast 12097 2048 KB Large Pages (24 GB)
  system wide to get 100% of the Shared
  Global Region allocated with Large pages
***********************************************************
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
Shared memory segment for instance monitoring created
Picked latch-free SCN scheme 3
Machine:x86_64
VM name:VMWare Version: 6
home_1/dbs/spfilepadb.ora
System parameters with non-default values:
  processes                = 500
  sessions                 = 780
  sga_target               = 24192M
  control_files            = "/u01/app/oracle/padb/control01.ctl"
  control_files            = "/u01/app/oracle/padb/control02.ctl"
  db_block_size            = 8192
  compatible               = "11.2.0.0.0"
  undo_tablespace          = "UNDOTBS1"
  remote_login_passwordfile= "EXCLUSIVE"
  db_domain                = ""
  dispatchers              = "(PROTOCOL=TCP) (SERVICE=padbXDB)"
  audit_file_dest          = "/u01/app/oracle/admin/padb/adump"
  audit_trail              = "DB"
  db_name                  = "padb"
  open_cursors             = 300
  pga_aggregate_target     = 8053M
  diagnostic_dest          = "/u01/app/oracle"
USER (ospid: 5117): terminating the instance due to error 119
ORACLE_HOME = /u01/app/oracle/product/11.2.0/dbhome_1
System name:Linux
Node name:padb
Release:2.6.32-573.el6.x86_64
Version:#1 SMP Wed Jul 1 18:23:37 EDT 2015
Machine:x86_64
VM name:VMWare Version: 6
Using parameter settings in server-side spfile /u01/app/oracle/product/11.2.0/dbb
home_1/dbs/spfilepadb.ora
System parameters with non-default values:
  processes                = 500
  sessions                 = 780
  sga_target               = 24192M
  control_files            = "/u01/app/oracle/padb/control01.ctl"
  control_files            = "/u01/app/oracle/padb/control02.ctl"
  db_block_size            = 8192
  compatible               = "11.2.0.0.0"
  undo_tablespace          = "UNDOTBS1"
  remote_login_passwordfile= "EXCLUSIVE"
  db_domain                = ""
  dispatchers              = "(PROTOCOL=TCP) (SERVICE=padbXDB)"
  audit_file_dest          = "/u01/app/oracle/admin/padb/adump"
  audit_trail              = "DB"
  db_name                  = "padb"
  open_cursors             = 300
  pga_aggregate_target     = 8053M
  diagnostic_dest          = "/u01/app/oracle"
USER (ospid: 5117): terminating the instance due to error 119
  remote_login_passwordfile= "EXCLUSIVE"
  db_domain                = ""
  dispatchers              = "(PROTOCOL=TCP) (SERVICE=padbXDB)"
  audit_file_dest          = "/u01/app/oracle/admin/padb/adump"
  audit_trail              = "DB"
  db_name                  = "padb"
  open_cursors             = 300
  pga_aggregate_target     = 8053M
  diagnostic_dest          = "/u01/app/oracle"
2018-07-12 09:45:28.043000 +08:00
USER (ospid: 18388): terminating the instance due to error 119
Instance terminated by USER, pid = 18388                           ############实例异常终止了
2018-07-12 09:47:53.701000 +08:00
Starting ORACLE instance (normal)
"/tmp/alert_5886_14061_padb_1.ado" 13117L, 632251C written

$df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                      627G  512G   84G  86% /
tmpfs                  32G   72K   32G   1% /dev/shm
/dev/sda1             477M   42M  410M  10% /boot

$
$sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Thu Jul 12 11:47:10 2018

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected.

SQL> startup
ORA-00119: invalid specification for system parameter LOCAL_LISTENER
ORA-00130: invalid listener address '(ADDRESS=(PROTOCOL=TCP)(HOST=padb)(PORT=1521))'
SQL> 

##########第一意识ping了一下主机名

$ping padb
ping: unknown host padb
$ping padb
ping: unknown host padb
$hostname
padb
$more /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

padb  10.18.0.84    ##到这里，只能无语了,外加18个点点点，这是啥啊！！！！
$ping padb
ping: unknown host padb
$exit
logout

####修改host文件
[root@padb ~]# vi /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
10.18.0.84  padb  

"/etc/hosts" 3L, 175C written
[root@padb ~]# 
[root@padb ~]# 
[root@padb ~]# ping padb
PING padb (10.18.0.84) 56(84) bytes of data.
64 bytes from padb (10.18.0.84): icmp_seq=1 ttl=64 time=0.029 ms
64 bytes from padb (10.18.0.84): icmp_seq=2 ttl=64 time=0.021 ms
^C
--- padb ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1804ms
rtt min/avg/max/mdev = 0.021/0.025/0.029/0.004 ms
[root@padb ~]# 

Refer to the SQL*Plus User's Guide and Reference for more information.
$sqlplus / as sysdba

SQL*Plus: Release 11.2.0.3.0 Production on Thu Jul 12 12:01:43 2018

Copyright (c) 1982, 2011, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup
ORACLE instance started.

Total System Global Area 2.5254E+10 bytes
Fixed Size                  2240096 bytes
Variable Size            3221225888 bytes
Database Buffers         2.2012E+10 bytes
Redo Buffers               18718720 bytes
Database mounted.
Database opened.
SQL> exit