Delay Between Filing and Writing Items to the Disk
There is always a delay between the time you execute the F (file) command from the Screen Editor and the time that the "filed" item is written to the disk. This is because the F command does not write the edited item out to disk, it only sets a write required flag for the affected memory buffers.
This delay is affected by the amount of main memory on your system and the amount of usage of the system and the main memory.