> For the complete documentation index, see [llms.txt](https://help.auxalia.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.auxalia.com/plant-tools/plantlink/how-to-use/usage/mapping-options.md).
# Mapping Options
This chapter describes the options you have on the **Mapping** page of the **PlantLink Wizard**.
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Not all options are available for all types of Link Configurations.
The project used in this chapter is based on the project created in [Create an Update Link](/plant-tools/plantlink/how-to-use/link-configurations/create-an-update-link.md). Please make sure that you are familiar with **Update Links** to better understand the options described below.
A link with the project created during this chapter is at the end of this chapter.
Write Back
Enabling **Write Back** you can override the mapped value in the Properties Palette, Data Manager, or PlantDataManager. Let's enable **Write Back** for the Description property.
Here we see die mapped data for both pumps.
Now we select just one pump and we change the Description.
When we save the drawing now, The previous mapped Description for the second pump is no out-of-date and therefore PlantLink wants us to select/update the data again.
Now the Description for the second pump has been updated.
Clear Value
By default, **Clear Value** is enabled, it means, that if PlantLink cannot find a suitable row in the table or view, or the user didn't select anything, then any value in the property will be deleted. This ensures, that there are no old values from previous mappings. This option can be used with or without a condition. A condition defines when a value should be cleared. For this example, we disable the checkbox **Clear Value** for the Model Number property.
If you change the type to a value for which there are no rows available, all properties with the exception of the Model Number are cleared.
When selecting P again, the **PlantLink - External Data Viewer** dialog pops up again and you can select a row.
The old **0001** value will be overridden with the new value.
Now we will define an expression. What we want to accomplish is, that the **Model Number** will be cleared only, if **Manual Data** is set to **Yes**. This allows you to later enter a value for **Model Number** which will not be cleared. For that you click on the square button right of the checkbox for **Clear Value**.
The **Expression Editor** opens.
We use the following expression. This expression means, that if the property **Manual Data** shows no, the condition is True, otherwise it's False. Meaning, that if **Manual Data** is **No** the value in **Model Number** will be cleared. Otherwise the value will not be cleared.
You can see the expression also in the tooltip.
Let's start with this case were data are mapped and **Manual Data** is **No**.
When we select a **Type** for which there are no data, the **Model Number** is cleared.
Now we select **P** again and select a row from the **PlantLink - External Data Viewer**. And now we change **Manual Data** to **Yes**.
If we select a type again for which there are no data, then the **Model Number** value stays.
Acquisition Mode Override
If a property is acquired, then PlantLink cannot map a value to this property. By default **Acquisition Mode Override** is disabled. When enabling this option PlantLink will change the **Acquisition Mode** to **Override** before mapping the value to the property. If the **Acquisition Mode** is set to **Override** and the mapped value is the same as the acquired value would be, then PlantLink will change the **Acquisition mode** back to **Acquire**. For this example, we have a second link configuration in this project for the **Hand Valves** class.
In the mapping page of the **Wizard** we check **Override Acquisition Mode**.
In the drawing we see, that the Ball Valve acquires the **Size** from the **PipeLineSegment**.
If we use **Assign Data** from the context menu of the valve symbol we now select a valve with a different size as the **PipeLineSegment**.
We see the new **Size** on the valve symbol and we see, that the **Acquisition Mode** for the **Size** property for the ball valve is set to **Override**.
Now we select a row from the table where the **Size** matches the **Size** of the **PipeLineSegment**.
Now we see, that the **Acquisition Mode** is set back to **Acquire**.
Sync Mode
**Sync Mode** controls when the mapped properties will be updated. Although PlantLink will instantly map the properties whenever you change the values used in the linked expression, there are cases where you might want to ensure, that the mapped properties are updated. The options are: 1.Never Mapped properties will not be updated. Unless you use [Update Link Configurations](/plant-tools/plantlink/how-to-use/usage/update-link-configurations.md) 2.On Drawing Open Mapped properties will be updated when the drawing is opened 3.On Drawing Save Mapped properties will be updated when the drawing is saved The list option is the commonly used one, because it ensured, that the mapped properties are always up-to-date when saving, or saving\&closing a drawing