Hi All,
hope someone can advise on this, I need to run 4 processes though only two are in use at any instance, but I need to swap between which are. Right now I pause a process then unpause the one I wish to use next. However I can have memory issues, that is I run out of RAM. So rather than reload each process from disk, which is slow, I thought I'd try to save load time by loading the process into RAM, then moving to swap space when not running. When I need it load from swap space to RAM again. Firstly is this possible? Secondly will it save time. Thanks in advance.

If I understand it well it is made automatically by the OS (if required).

Yes, and the kernel is smarter. For example, you have one program that uses some code segments and some data segments. Writing the code segment to swap is pointless as the code already is on disk. So the kernel will simply drop the code segment when more RAM is needed, and load it back later later. Moving the code to swap makes no sense.

So rather than reload each process from disk, which is slow, you want to put it on disk but it feels better when the region where you put it is called swap?
make it simple ,
dump the data of unused processes to disk and put the process to sleep, if you have luck they are in the disk cache and fast swapping between the processes is not an issue, or it is in /tmp which is mounted to tempfs anyway :-), however, if is on disk it depends if reading form file is not very noticeable faster or slower than from swap.