ORA-15055 ASM Diskgroup Status Showing Dismounted From RDBMS Instance

在数据库实例中检查asm 磁盘组的状态时，显示 DISMOUNTED,但是在asm 实例上却显示MOUNTED
在数据库实例的alert 日志中会出现如下信息：

SUCCESS: diskgroup ASMDISK02 was mounted
SUCCESS: diskgroup ASMDISK02 was dismounted
SUCCESS: diskgroup ASMDISK02 was mounted
SUCCESS: diskgroup ASMDISK02 was dismounted
SUCCESS: diskgroup ASMDISK02 was mounted

ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '+ASMDISK01/cnf2/redo01.log'
ORA-17503: ksfdopn:2 Failed to open file +ASMDISK01/cnf2/redo01.log
ORA-15055: unable to connect to ASM instance
ORA-00020: maximum number of processes () exceeded
ORA-15055: unable to connect to ASM instance
ORA-00020: maximum number of processes () exceeded
ORA-00313: open failed for members of log group 1 of thread 1
ORA-00312: online log 1 thread 1: '+ASMDISK01/cnf2/redo01.log'
ORA-17503: ksfdopn:2 Failed to open file +ASMDISK01/cnf2/redo01.log
ORA-12549: TNS:operating system resource quota exceeded

原因：
这个问题是由于数据库实例不能和asm 实例进行通讯，不管何时尝试连接asm，它都用尽os 资源。在系统级别上不能创建新的进程。
在 数据库实例上检查磁盘组的状态：
SQL > select name,state from v$asm_diskgroup;

NAME                                  STATE
------------------------------    -----------
ASMDISK01                       CONNECTED
ASMDISK02                       DISMOUNTED

CONNECTED 意味着数据库实例正在使用这个磁盘组
DISMOUNTED 意味着数据库实例将磁盘组视为不可用。

解决办法：
在这种情况下由于asm 进程数已经达到上限，新的asm进程不能创建导致数据库实例不能够连接到asm上。默认的ASM进程数为40，可以将 进程相关的参数设置为更高一些 比如150