Configuring the Memory Reserve for an Online Change
You can configure a function block with a memory reserve to prevent its function block instances from having to be copied to new memory locations during an online change. This can happen when you make declaration changes for example adding variables to the function block. With memory reserves, this kind of online change runs faster and fewer problems occur. When the memory reserve is depleted, a message is displayed before the online change is performed.
Important
The memory reserve for a function block is best configured before downloading the application to the controller for the first time. If the memory reserve is configured when the application exists on the controller, then a more complicated online change is necessary.
Configuring a memory reserve for the online change for a function
In the future, bigger changes are made to a function block of a project, which could result in function block instances being copied to other memory locations in an online change.
Requirement: The open project is not located on the controller yet.
Click Online Change Memory Reserve Settings.
The Online Change Memory Reserve view opens.
Select the application of the project from the list box.
Click .
Click the Scan Application button.
Select the All entry in the Function Blocks area.
All function blocks of the application are displayed in the view.
Select the corresponding function block for which you want to configure a memory reserve.
If the application is not on the controller yet, then the Memory Reserve field is editable (in bytes).
If the application is already on the controller, then click the Enabled button in the Enable Editing area.
Note that if you modify the memory reserve of an application that is already on the controller, then the instances of all affected function blocks have to be copied to the memory.
Specify the size of the memory reserve (in bytes) and click Apply for Selection.
The given number of bytes is shown in the Memory Reserve field in the table.
Click and then click Scan Application.
The following information is updated in the function block list for the configured function block: Size, Number of Instances, Additional Memory for All Instances, and Remaining Size of Memory Reserve.
Now when you download the application to the controller, the function block instances occupy the required memory and also the memory reserve. In the future, bigger changes of the function block can be downloaded to the controller with the online change without having to copy all function block instances to memory.