Is there a trick to reserve a percentage of actual RAM to be used for investigations and fixes? Because unless you already have a working shell open on the mach

Is there a trick to reserve a percentage of actual RAM to be used for investigations and fixes? Because unless you already have a working shell open on the machine etc, are you going to wait 10 minutes for ssh to spawn a child, then 10 minutes for the shell to load and give it another 5 minutes for your ps to show?