Low memory

Low Memory Errors

The message you see may appear from time to time because other applications may still be running in the background taking up memory. If the app you are trying to use is hungry for memory you may see this message appear. Turning off your iPhone and then back on reloads OSX and reclaims memory that might have been being used by the open applications.

Tera

 

+1 for good answer

 

Powering the phone off 'reclaims memory' because it terminates all tasks, including any that were running in the background. If there are errors in the app, i.e., it allocates memory but doesn't free it when the app ends, can cause the out of memory error, too. Perhaps the iPhone opsys doesn't trust apps to free all memory and does it for them.

This is an issue with apps that run in the background, either because they have this feature built in or because Backgrounder was used, they take up memory and, depending on the app, might also be using processor cycles.