Configuring the memory reserve for Online Change

You can configure a memory reserve for the online change for function blocks. This means that, provided the memory reserve is sufficiently large, after changes have been made to the declaration of a function block during the subsequent online change, the instances of the function block do not have to be copied to new storage spaces. This refers primarily to online changes in which one or more new variables are added to a function block. If the function block instances do not have to be copied to new storage spaces due to the memory reserve, the online change is faster and fewer problems occur. When the memory reserve is exhausted, a message appears before the online change is performed.

Configuring the memory reserve for Online Change 1:

Configuration of the memory reserve before the first download

It is best to configure the memory reserve for a function block before downloading the PLC project to the controller for the first time. If the memory reserve is only configured when the PLC project is already on the controller, a complex online change is necessary.

Configuring the memory reserve for Online Change 2:

Alternative configuration option

As an alternative to the Online Change Memory Reserve Settings window, the memory reserve per function block can also be configured in the properties window. To do this, the function block must be selected in the project tree.

Configuring a memory reserve for a function block for the online change

In the future, major changes are to be made to a function block of the project. This would require copying the function block instances to other storage locations during online change.
Ideally, the open project is not yet on the controller.
1. From the PLC menu, select Window > Online Change Memory Reserve Settings.
The Online Change Memory Reserve view opens.
2. Select the PLC project from the selection list.
3. From the Build menu, choose Build.
4. Click the Browse application button.
5. Select the "All" entry in the "Function blocks" area.
All function blocks of the PLC project are displayed in the view.
6. Select the function blocks for which you want to configure a memory reserve.
If the application is not yet on the controller, the input field "Memory reserve (in bytes)" can be edited.
7. If a PLC project is already on the controller, click on the Allow button in the "Allow editing" area.
Note that if you change the memory reserve of a PLC project that is already on the controller, the instances of all affected function blocks must be copied in memory.
8. Enter the size of the memory reserve in bytes and click Apply to selection.
The number of bytes entered is displayed in the table in the Memory reserve field.
9. From the Build menu, choose Build.
10. Click the Browse application button.
In the function block list for the configured function block, the information "Size", "Number of instances", "Additional memory for all instances" and "Remaining memory reserve size" are updated.
11. Load the PLC project into the controller.
The function block instances occupy the currently required memory and additionally the memory reserve. Future major changes to the function blocks can thus be loaded to the controller via the online change without all instances of the function blocks having to be recopied in the memory.

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