Managed versus external assets in Unity Catalog
Every securable object that you register in Unity Catalog is centrally governed. This means that Unity Catalog manages the object's metadata, allowing it to control all aspects of governance including access, auditing, and lineage.
However, for data assets like tables and volumes, Unity Catalog can also control the storage location and lifecycle of the underlying data files in your cloud account, which includes how they are organized, optimized, and when they are deleted. This distinction is what separates managed from external data assets.
- Managed assets: Unity Catalog controls both governance (access control, auditing, lineage) and the underlying file storage lifecycle (file optimization, how they are organized, and when they are deleted).
- External assets: Unity Catalog controls governance only. The underlying file storage lifecycle is controlled by you or an external system.
When you register a managed asset in Unity Catalog, you retain full ownership of your data. The data files always remain in your cloud account. Unity Catalog determines where within your account they are stored, but does not transfer them to Databricks or own them.
The distinction between managed and external applies to tables and volumes only. Other Unity Catalog securable objects, such as views, models, and functions, do not have managed and external variants.
Summary of differences
The following table summarizes the differences between managed and external assets in Unity Catalog:
Unity Catalog managed table or volume | External table or volume | |
|---|---|---|
Storage location | Set by Unity Catalog (in your cloud account) | Set by you |
File lifecycle management | Managed by Unity Catalog (optimization, organization, deletion) | Managed by you |
Drop behavior | Data files are permanently deleted | Data files remain in place |
Data ownership | Yes | Yes |
Uses of the word "manage" across Unity Catalog
The word manage has multiple uses across Unity Catalog. This section summarizes the meaning of manage in different contexts.
When people say that an object is managed by Unity Catalog, they typically mean that Unity Catalog governs access to it. This applies to all registered Unity Catalog objects, including external tables and volumes.
The word managed in "managed table" or "managed volume" has a more specific meaning: Unity Catalog determines where in your cloud account the underlying data files are stored, and controls the file lifecycle (optimization, organization, and deletion). This is referred to as managed storage. Your data remains in your cloud account at all times; Databricks does not own or hold your data.
The word MANAGE also appears as a privilege that you can assign to Unity Catalog objects. Generally, MANAGE allows a user to assign or revoke privileges on, transfer ownership of, and delete an object without being the owner. See MANAGE.
The following table summarizes these common uses of manage:
Term | Meaning | Applies to |
|---|---|---|
"Managed by Unity Catalog" | Unity Catalog governs access, auditing, and lineage for the object. | All registered Unity Catalog objects, including external tables and volumes |
Managed table or managed volume | Unity Catalog also controls the underlying storage location (managed storage) and data lifecycle within your cloud account. | Tables and volumes only |
Managed storage | A designated path within your cloud account where Unity Catalog stores data files for managed tables and volumes. Managed storage is not Databricks-owned infrastructure — you configure the location at the metastore, catalog, or schema level. See Specify a managed storage location in Unity Catalog. | Tables and volumes only |
| A privilege that allows a user to assign or revoke privileges on, transfer ownership of, and delete an object without being the owner. See MANAGE. | All Unity Catalog securable objects |
Managed and external tables
A Unity Catalog managed table is a table where Unity Catalog determines the storage location for the underlying data files. Unity Catalog stores managed tables in the managed storage location defined on the containing schema, catalog, or metastore. When you drop a managed table, Unity Catalog deletes the underlying data files. Managed tables use the Delta or Apache Iceberg format.
An external table is a table where you specify the storage location for the underlying data files. When you drop an external table, Unity Catalog removes the table metadata from the metastore, but the underlying data files remain in place. External tables support multiple formats, including Delta, CSV, JSON, Avro, Parquet, and ORC.
For more information about table types, see Databricks Unity Catalog table types.
Managed and external volumes
A Unity Catalog managed volume is a volume where Unity Catalog determines the storage location. Unity Catalog automatically stores managed volumes in the managed storage location of the containing schema within your cloud account. As with managed tables, you retain full ownership of the underlying data. When you drop a managed volume, Unity Catalog deletes the underlying data files.
An external volume is a volume where you specify the storage location. The location must be a path covered by a Unity Catalog external location. When you drop an external volume, Unity Catalog removes the volume definition, but the underlying data files remain in place.
For more information about volumes, see What are Unity Catalog volumes?.