1.Please edit the NmsProcessesBE.conf file in OpManager\conf folder and search for the text CLEAN_DATA_INTERVAL 999999 .
2.Paste GENERATE_DATACOLL_EVENT true right after that.
For example :
CLEAN_DATA_INTERVAL 999999 GENERATE_DATACOLL_EVENT true
3.Save this file and restart OpManager service.
Disclaimer: There is no option to choose the devices and it will send alarms even for the wrong monitors. So there is a chance of alarm flooding. If you are not interested, it should be updated as false