---
title: "Implications of Overwriting Data in BigPicture Field Mapping Changes"
canonical: "https://support.appfire.com/space/SUPPORT/3711074377/Implications%20of%20Overwriting%20Data%20in%20BigPicture%20Field%20Mapping%20Changes"
format: markdown
---
## Summary

This article explains the implications of the warning message: *"Are you sure? Your Jira Server issue data will be overwritten with BigPicture data. You can't undo this action"* when changing field mappings in BigPicture. It covers the risks of data overwriting and how to handle empty values during synchronization.

## Overview

When modifying the **Start/End Date field mapping** in BigPicture (e.g., changing the mapping from a custom field to the Jira **Due Date**), BigPicture displays a warning about data being overwritten. This is because changing the mapping is not merely a display preference; it changes the source of truth for task synchronization.

## Use Case 1: Changing Field Mappings (e.g., End Date to Due Date)

When you change the mapping of a date field, BigPicture synchronizes the dates it currently holds for tasks into the newly mapped Jira field.

### Risk: Data Overwriting

- **What happens:** If BigPicture has a stored date for a task and you map it to a new Jira field (like `Due Date`), BigPicture will write its stored value into that Jira field.
- **Consequence:** Any existing data in the newly mapped Jira field will be replaced by the BigPicture value. This action is irreversible.
- **Why it might seem like "nothing happened":** In test environments, you might not notice a change if:
  - The BigPicture values and Jira field values were already identical.
  - The scope of the change was small.
  - There were no conflicting values.

### Recommended Action

Before applying mapping changes in a production environment:

1. Compare the current **BigPicture End Date** values with the existing **Due Date** (or target field) values for a representative set of issues.
2. Ensure that overwriting the target Jira field with BigPicture data is acceptable for your project.

## Use Case 2: Handling Empty Values During Mapping Changes

A common question is whether an empty value in BigPicture will erase an existing value in the newly mapped Jira field.

### Risk: Potential Data Loss

- **Behavior:** You should **not** assume that an empty BigPicture date will leave an existing Jira field value unchanged.
- **Consequence:** There is a potential risk that existing Jira field values (e.g., `Due Date`) could be cleared or affected if the corresponding BigPicture value is empty during the synchronization process triggered by the mapping change.

### Recommended Action

- Verify if tasks in BigPicture have populated dates before remapping to a Jira field that already contains critical data.
- Always perform a backup or test the specific scenario with a subset of data if you are concerned about losing existing Jira field values.