---
schema_version: "1"
id: 5a1346007d0abaf498c7a6227858ab2643591ca7ee2266f785aabe81abd693c0
title: External Change Data Capture Considerations
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/platform/264-0-0/external_object_change_tracking_considerations.md
canonical_url: https://help.salesforce.com/s/articleView?id=platform.external_object_change_tracking_considerations.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: ce8f2371ff5c8531191ca7ba8a1a893bffc58276a391320459c8a9a09594315d
description: Keep these considerations in mind when working with External Change Data Capture.
products:
  - Salesforce Platform
  - Security
release: "264"
---
# External Change Data Capture Considerations

Keep these considerations in mind when working with External Change Data Capture.

- Each polling request counts toward your Salesforce org’s OData callout rate allocation.
- OData doesn’t differentiate between created and updated change events. Both events are published with update change type.
- When you enable change tracking, a $top=0 query for zero rows is sent to the external data source to tell it to track changes, and a delta link is returned.
- If an error occurs, Salesforce stops sending polling requests. You can check for an error status by querying the BackgroundOperation object or viewing the latest error on the object’s setup page.
- If you create an Apex trigger to respond to change events, these requirements and behaviors apply.
    - Create the Apex trigger with development tools, such as the Developer Console or Metadata API or Salesforce UI. You can’t create the trigger from the Salesforce UI.
    - Because the Apex trigger runs after an event occurs, only the after-insert trigger event is supported.
    - The trigger passes the associated change event, not the object that caused the change.
    - Changed records can be committed in the same transaction that started the trigger. However, keep in mind that this transaction is separate from the transaction that created the original event.