What are the disadvantages of swapping technique used in pre-3BSD UNIX systems?
- If there is excessively much memory contention, processes are swapped out until sufficient memory is available.
- As well, a few large processes are able to force many large processes out of memory.
- A process bigger than non-kernel main memory cannot run at all.
- User data segment and System data segment are kept back in contiguous main memory locations for swap-transfer efficiency, thus external fragmentation is a serious problem.
- Throughput of the system is little compared with paged systems.