Restriction rules allow certain users to access only the records that are essential to their work. To apply this layer of security to data that’s stored outside your Salesforce org, set a restriction rule on external object records.
Where: Restriction rules are available in Lightning Experience in Enterprise, Performance, Unlimited, and Developer editions. External objects are available with Salesforce Connect and Files Connect.
How: To create and manage restriction rules for external object records, add a restriction rule from the External Data Sources page in Setup. Only external objects created using the Salesforce Connect: OData 2.0, OData 4.0, and Cross-Org adapters support restriction rules.
External objects don’t appear in Object Manager. To navigate to an external object, from Setup, in the Quick Find box, enter External Data Sources, and then select External Data Sources. Select an external object from the list view on this page. Or find external objects in the Most Recently Used list in Setup.
Admins are responsible for ensuring that rules they create on external objects don’t negatively impact performance in Salesforce or in the external system.