You can use this pragma to prevent the instance of a function block from being stored in the retain memory.

Syntax:

{attribute 'no_instance_in_retain'} 

Insert location:

Lines above the ‎FUNCTION_BLOCK‎ declaration in the declaration part of the function block.

Now when you declare an instance declaration of the function block as a ‎RETAIN‎ variable, an error message is issued.