If you don't need the web services you publish to access your source data, ArcGIS Server can copy the service data when you publish. The copy of the data is placed in a location that is accessible to the ArcGIS Server site.
Copying data when you publish can be useful when your source data is behind a firewall but the web services are not. It can also help you keep your internally edited datasets separate from the ones you make available through web services. Copying the data ensures that the service you publish (for example, a map service) will have no trouble accessing its source datasets.
Data will be copied from the source when you publish a map service (map image layer) from ArcGIS Pro and the data source is not registered with the ArcGIS Server site. The copied data is placed in a folder on one of the machines in the ArcGIS Server site.
Tip:
When you publish to ArcGIS Online, data is always copied. If you publish to an ArcGIS Enterprise portal with the Copy all data option enabled, data will also be copied from the data source.
Best practices for copying data
Copying large amounts of data can take several hours or longer. To avoid copying an excessive amount of data, examine whether there are any nonessential layers in your map that could be removed before you publish.
Whenever copying data to the server, ensure that the ArcGIS Server machine has enough available disk space to receive the copy. This space may be larger than you anticipate if you fail to account for the size of all the layers in the service at the full extent of the service.
Datasets that cannot be copied
Some types of data cannot be copied to the server as part of the publishing process. These include selection layers, custom layers, video layers, and tool layers.
Disabling the ability to copy data when publishing
If you're an ArcGIS Server administrator and you want to prevent publishers from automatically copying data to the ArcGIS Server site when they publish, you can disable data copying using ArcGIS Server Manager. You might do this to prevent publishers from filling up the disk space on the machines in the ArcGIS Server site. For instructions, see Disable automatic data copying when publishing to ArcGIS Server.