Oracle问题：ORA-12528: TNS: 监听程序: 所有适用例程都无法建立新连接
问题原始描述：
ORA-12528: TNS:listener: all appropriate instances are blocking new connections
发现问题：
通过在CMD下用lsnrctl status 查看出的问题：发现BLOCKED；
然后：尝试启动oracle数据库：
[root@MyYun ~]# su - oracle
Last login: Thu Jul 18 22:01:58 CST 2019 on pts/1
[oracle@MyYun ~]$ sqlplus / as sysdba
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 1068937216 bytes
Fixed Size 2220200 bytes
Variable Size 394268504 bytes
Database Buffers 666894336 bytes
Redo Buffers 5554176 bytes
SQL> select status from v$instance;
STATUS
------------
STARTED
SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
执行上代码块的操作后，在本地使用第三方链接工具链接Oracle数据库时就出现了ORA-12528错误。
解决办法如下：
相继执行如下命令：
[oracle@MyYun~]$ sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Thu Jul 18 22:55:06 2019
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Connected to an idle instance.
SQL> shutdown;
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
SQL> startup
ORACLE instance started.
Total System Global Area 1068937216 bytes
Fixed Size 2220200 bytes
Variable Size 394268504 bytes
Database Buffers 666894336 bytes
Redo Buffers 5554176 bytes
Database mounted.
exDatabase opened.
SQL> exit;
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
命令解释：
- shutdown命令： 相当于以下三个命令
normal;
shutdown immediate;
shutdown abort;
- startup命令： 等于以下三个命令
startup nomount;
alter database mount;
alter database open;