Hi Tuan
I think you have to go to each device, if you go to Devices / operations and then select the device from the lefthand view then in the middle view
![3baddab0804c42bd84ad0cc6990abb61_RackMultipart20170724-12222-3wzmlo-filecrash_inline.jpg 3baddab0804c42bd84ad0cc6990abb61_RackMultipart20170724-12222-3wzmlo-filecrash_inline.jpg](/t5/image/serverpage/image-id/5638i93A28ABB4BBA42D0/image-size/large?v=v2&px=999)
the crash file will appear under filename, highlight it and select delete at the bottom, Some on the crash files I had were from 2016, so filed them in B1N