今天连接oracle报错：ORA-27101: shared memory realm does not exist，排查过程如下：

1、查看内存是否有空余：

free

内存如下，说明内存好的：

2、查看磁盘是否有空余：

df -h

发现磁盘已经满了,有可能磁盘满了导致服务停了

3、用 "du -h --max-depth=1 "命令，最终定位到是redis日志占了20g，删掉redis日志后，执行如下命令

[root@k8s-master log]# su -l oracle
Last login: Tue Jul  2 10:27:46 CST 2019 on pts/0
-bash: /etc/profile: Permission denied
-bash: /etc/profile: line 53: syntax error near unexpected token `then'
-bash: /etc/profile: line 53: `if[ $USER = "oracle" ]; then'
[oracle@k8s-master ~]$ sqlplus /nolog

SQL*Plus: Release 12.1.0.2.0 Production on Tue Jul 2 10:46:25 2019

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

SQL> connect / as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.

Total System Global Area 2449473536 bytes
Fixed Size		    2927336 bytes
Variable Size		  654312728 bytes
Database Buffers	 1778384896 bytes
Redo Buffers		   13848576 bytes
Database mounted.
Database opened.
SQL> 

4、再次连接oracle，一切正常