If your computer runs out of physical main memory and has no swap space to fall back on, it will
start to kill user space processes¹ (and it's hard to predict which ones) to accommodate memory needs of the kernel and
behave erratically, because memory allocation for user space processes¹ will fail, which most applications aren't programmed to anticipate; this usually leads to crashes because these applications then try to access invalid memory addresses.
tapi, jangan khawatir, linux ada teknik OOM. which rather than stopping the kernel when it runs out of memory, will start to kill of processes to free resources. Its actions are configurable.