The drawbacks of fixed partitioning are:
- The number of partitions are précised at system generation time limits the number of active processes in the system.
- For the reason that partition sizes are preset at system generation time, small jobs will not make use of partition space efficiently. In an environment wherever the main storage requirement of all jobs is known beforehand, this perhaps reasonable, although in many cases, it is an incompetent technique.
The use of portioning is approximately unknown today. An instance of OS which use this technique was an IBM mainframe operating system OS/MFT.