Error notification support for SIGDANGER signal

The AIX® Virtual Memory Manager (VMM) uses a combination of physical memory and disk storage to provide a virtualized memory space that is much larger than the actual physical memory.

The storage-based component of this system is called the paging space. If not enough paging space is configured or available, the systems performance can be diminished and certain system functions might begin to fail. In a high availability environment, you want to avoid this situation because it might lead to false failovers or failures during recovery of critical resources.

When paging space becomes too low, the AIX operating system generates a SIGDANGER signal for processes that are running on the system, including the PowerHA® SystemMirror® subsystems. When the PowerHA SystemMirror cluster manager or clstrmgr subsystem receives a SIGDANGER signal it creates an entry in the AIX system error log. You can create a notification method that is called whenever this situation occurs. You can use this notification method to configure an automatic response when the paging space becomes too low. The response from the notification method can be as simple as sending an alert to the system administrator, or as complex as automatically recovering the page space.

To define an error notification to run when PowerHA SystemMirror receives a SIGDANGER signal, you need to create an entry in the errnotify odm class. Use the odmadd command with a file that contains the following information to update the odm class:
errnotify:
        		 en_name = "ha_sigdanger"
        		 en_persistenceflg = 1
        		 en_resource = "clstrmgrDANGER"
        		 en_method = "errpt -a -l $1 | mail -s 'SIGDANGER received' root"
Note: You can customize other aspects of the notification method. For example, the en_method field can specify a shell script or other executable program. For this notification method to work, you must specify the clstrmgrDANGER setting in the en_resource field.

You can change the notification method entry by using the odmchange command. You can remove the notification method entry by using the odmdelete command.