---
schema_version: "1"
id: ec8cd6e9b5bec10d0900d6c817516b1034b090beb446ae534703ff325d320dd5
title: Events and Data Extensions
collection: admin
version: current
locale: en-us
portal_url: https://docs.salesforce.com/admin/current/en-us/mktg/264-0-0/mc_jb_entry_events_data_extensions.md
canonical_url: https://help.salesforce.com/s/articleView?id=mktg.mc_jb_entry_events_data_extensions.htm&release=264.0.0&type=5
source_site: help.salesforce.com
content_type: documentation
content_hash: 5ffa40e6899de6033649d23aa79cb86d1fb8b535d8cd5e488f9dd29edc3f2d70
description: When a journey's entry source is configured in Journey Builder, the data source from which contacts are admitted is usually a data extension.
products:
  - Marketing
  - Marketing Cloud Engagement
release: "264"
---
# Events and Data Extensions

When a journey's entry source is configured in Journey Builder, the data source from which contacts are admitted is usually a data extension.

When an event fires, Journey Builder admits the contacts stored in the entry source data extension that meet entry criteria. Specifically, Journey Builder evaluates the data extension from its first row and continues until all existing rows are evaluated.

The next time the event fires, the entry source begins evaluating rows from the point where it stopped. This factor prevents contacts that are already in the journey from entering the same journey again if their contact record is unchanged.

## Single Event Source for Multiple Events

Multiple entry sources can use the same data extension.

Three methods exist for admitting contacts into a journey.

- API
- Automation Studio’s Fire Event activity
- The Schedule feature found within Journey Builder’s event setup process

Ensure that the desired contacts enter each journey as intended. Use one of these three methods to admit contacts from an event source data extension.

Journey Builder now evaluates the event source data extension separately for each individual event.

## Events and Shared Data Extensions

A shared data extension can be used as the entry source data extension in more than one business unit. Journey Builder separates the processing of the data extension for each business unit. Events that run against a data extension in Business Unit A evaluate records starting at the last row that was evaluated previously. But when an entry source uses this data extension in Business Unit B for the first time, it begins at the first row.

#### See Also

- [Create a Data Extension in Contact Builder](https://help.salesforce.com/s/articleView?id=mktg.mc_cab_create_a_new_data_extension.htm&language=en_US)
- [Business Units in Marketing Cloud Engagement](https://help.salesforce.com/s/articleView?id=mktg.mc_es_business_units.htm&language=en_US)