---
title: How to define a fallback behavior?
description: To enable data synchronization between two systems, the properties of the data must be linked so that ChurchTools knows which property in ChurchTools corresponds to which property in the external system and can be synchronized. They are linked into what…
url: "https://staging.churchtools.academy/en/help/churchtools-modules/configure-connections/how-to-define-a-fallback-behavior/"
updated: "2026-08-25"
category: Sync / Configure Connections
---

# How to define a fallback behavior?

To enable data synchronization between two systems, the properties of the data must be linked so that ChurchTools knows which property in ChurchTools corresponds to which property in the external system and can be synchronized. They are linked into what are called *property pairs*. The property pairs always apply to the entire connection.

Some of these properties have *values* that must also be linked to one another; for example, the " *gender* " property has the values " *unknown*," " *male*," " *female*," and possibly " *diverse*."

If not all values in a property pair are linked—that is, if the link is incomplete—this will prevent the execution of all sync jobs for which you have selected that property pair.

To prevent this, you can define a **fallback behavior** for the relevant values. This allows you, for example, to synchronize the data first and then review the data assigned here in ChurchTools later to ensure it is correctly mapped. In this article, we’ll show you how to define a fallback behavior.

**Note**

If you have created a connection that supports writing in both directions, you can define fallback behavior for both directions. If your connection supports writing in only one direction, you can define fallback behavior for only one of the connected systems.

## Call a connection with an incomplete value mapping

Navigate to a *connection* (1) with an incomplete value mapping for which you need to define a fallback behavior. On the right side, you’ll see *a message indicating* that *synchronization* is *being prevented* (2) because the value mapping is incomplete. Click *“Edit Value Mapping”* (3) here.

[![Screenshot Sync Execution prevented](https://staging.churchtools.academy/wp-content/uploads/2025/06/Sync_Execution-prevented.png)](https://staging.churchtools.academy/wp-content/uploads/2025/06/Sync_Execution-prevented.png)

**Note**

There are property pairs for which you must first assign a parent date before you can actually assign the values. Examples include roles for groups or accounts, and cost centers by fiscal year.

![Screenshot: Assign Values, Assign Parent Date](https://staging.churchtools.academy/wp-content/uploads/2025/06/CleanShot-2025-08-14-at-14.02.15-1.png)

Once you've assigned the parent date, a yellow *"Assign Values*" button will appear, which you can use to assign the values as described below.

![](https://staging.churchtools.academy/wp-content/uploads/2025/06/CleanShot-2025-08-14-at-14.02.36.png)

## Define fallback behavior

In the value mapping, click the *red exclamation mark* (4) that *appears*next to " *Not linked*."

[![Screenshot Sync Execution prevented Edit gender](https://staging.churchtools.academy/wp-content/uploads/2025/06/Sync_Execution-prevented_Edit-gender.png)](https://staging.churchtools.academy/wp-content/uploads/2025/06/Sync_Execution-prevented_Edit-gender.png)

When defining the fallback behavior, you have the option *to assign* a *fallback value* (1), *clear* the *property* (2), or define *protected values* (3) that should not be overwritten by a fallback value even if they are not linked. You can delete an existing fallback behavior by clicking *Delete Fallback* (4).

[![Screenshot Sync Execution prevented Edit gender Define fallback](https://staging.churchtools.academy/wp-content/uploads/2025/06/Sync_Execution-prevented_Edit-gender_Define-fallback.png)](https://staging.churchtools.academy/wp-content/uploads/2025/06/Sync_Execution-prevented_Edit-gender_Define-fallback.png)

## Read more

- [How to synchronize my data?](https://staging.churchtools.academy/en/help/churchtools-modules/basics-sync/how-to-synchronize-my-data/)
- [How to form pairs of properties?](https://staging.churchtools.academy/de/help/churchtools-module/verbindungen-konfigurieren/wie-bilde-ich-eigenschaften-paare/)