This error message appears when online modification memory consumption is more than the value at "Free Data Memory" in Project Setting--> Build--> Free data memory.

This is an extra reserved memory for unallocated variables during online modification. The default value is 1kbytes. User can increase this value to max 64kbytes.

Every new unallocated variable is added to internal memory buffer. This memory is not cleaned after Build Changes.

If  variables are added for a certain time this memory can overflow because every new variable needs additional memory. It is only cleaned by BUILD ALL which causes a stop of the PLC.

Then the variables are put in the normal structure of the other unallocated variables and this memory is free.

But somtimes 64 kBytes can be too small for large structures. All new defined variables are saved in this area until you make a "Rebuild all Project".

Solutions for this problem:

- UnityPro V5.0: will show a message if 75 % of the data memory is used.

- UnityPro V6.0: A final solution is planned. After this error should no longer occur.