dl-breadcrumbs__homedl-breadcrumb-item__separatorConfiguration and programmingdl-breadcrumb-item__separatorProgramming with CODESYSdl-breadcrumb-item__separatorAutomation Builderdl-breadcrumb-item__separator...dl-breadcrumb-item__separatorReference: User Interface dl-breadcrumb-item__separatorMenu Commands dl-breadcrumb-item__separatorOnline dl-breadcrumb-item__separatorCommand: Online Change dl-breadcrumb-item__separatorWhat prevents an online change?
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In CODESYS, there are actions after which an online change on a controller is no longer possible. After that, the application always has to be completely recompiled. A typical case is the ⮫ Clean All command which deletes the compile information stored at the last download. However, these kind of actions typically generate a warning which you have to acknowledge.

But there are also "normal" editing actions which result in an online change not being possible at the next login. Therefore, you need to pay attention to the following symbol in the status bar when editing in the program POUs: _cds_icon_online_change_ok.png. When this symbol turns red in color _cds_icon_online_change_nok.png, only a full download to the controller can be performed. Double-click the symbol to open the “Application Information” dialog with a list of differences from the last download. In the dialog, you also find information about which of the changes prevent an online change.

For more information, see: ⮫ Command: Login

Table 620: Actions and changes in different areas of an application which prevent an online change:

Check functions

Activation or removal of a check function (‎CheckBounds‎, ‎CheckRange‎, ‎CheckDiv‎, etc.)

Change in an interface of a check function (also the insertion and deletion of local variables)

Task Configuration

Change in the configuration settings

Project Settings

Change of the “Compile Options” in the “Settings” section (Unicode, replace constants, logging in, breakpoints)

Change in the “Compiler defines”

Application properties

Change of the “Target system memory settings” (“Build” tab)

POU properties

Change of the “External implementation” option (“Build” tab)

Tasklocal global variable list

All changes

Function block

Change of the basis POU of a function block (‎EXTENDS FBbase‎), also the insertion or deletion of such a basis POU

Change in the interface list (‎IMPLEMENTS ITF‎)

Exception: Adding a new interface at the end of a list

Data Type

Change of the data type of a variable from one custom data type to another custom data type (for example, from ‎TON‎ to ‎TOF‎)

Change of the data type from one custom data type to a basis type (for example, from ‎TON‎ to ‎TIME‎)

Note: As a workaround, you should always change the name of the variable together with the data type. Then the variable is initialized as a new variable and the old one is removed. After that, an online change is possible.

Alarm Configuration

Change in the alarm database configuration

Change of the number of latch variables (also has an impact on the memory format in the database)

Change to the configuration of the distributed alarms

Data Source

All changes in the configuration

Device configuration

Change in the device tree (also by means of the “Update Device” command)

Change in a device configuration: By default, changes to device parameters are not capable of online change. However, exceptions can be configured in the device description.

Note: I/O mapping to variables is possible by means of an online change.

Visualization

Toggling of the overlay function

Before V3.5 SP6: Change in the configuration of the trace element

Note: In V3.5 SP6 and higher, the following applies: For online changes which affect visualizations or affect the data of the application (for example, a new variable is inserted), the visualization is completely reinitialized. For TargetVisu, for example, this means that the visualization closes and reopens with the start page. For WebVisu, the visualization also restarts with the start visualization after a short waiting period.

Unit Conversion

Insertion or removal of objects for unit conversion

Trend

Change of the number of variables or maximum number of variables

Change of the number of variables with a description or special line settings

For more information, see: ⮫ “Performing an Online Change ” and ⮫ “Attribute: init_on_onlchange ”