After installing nw 6.5 sp5 I had some memory problems so I did the

set auto tune server memory = off
set file cache maximum size = 2147483648

and reset the server. However, after that I have problems with backing up
server's file system files either with the BackupExec or sbcon. In both
cases server crashes after a couple of minutes doing backup so I wonder if
this memory tuning settings caused this to happen.