Please refer Advisory
"Aruba 600 Series Branch Office Controller Out-of-Memory Support Advisory - SA-20160621 - Tuesday, June 21, 2016"
http://support.arubanetworks.com/Announcements/tabid/139/Default.aspx
Which talks about the Out of memory issue on Aruba 600 series controller.
Note: You should login to support site to view the Advisory.