Feature Layer (existing)

The Feature Layer (existing) output in ArcGIS Velocity allows you to write output features to an existing ArcGIS Velocity layer, an existing ArcGIS Online hosted feature layer, or an existing ArcGIS Server feature layer. When using this output type, features will be written to an existing feature layer, as opposed to creating a feature layer. The existing feature layer should be of the same geometry type and contain all of the same attributes and field tags as the incoming data.

Examples

• After ingesting real-time features from IoT sensors through a feed and a real-time analytic, an asset manager wants to add those observations to an existing feature layer.
• A GIS analyst performs analysis of the latest information in a big data analytic and appends the results to an existing layer that is already in use in various applications.
• A business analyst ingests a set of existing, historical observations from an external cloud store and configures a real-time analytic to process events as they occur and captures the new observations in an existing feature layer.

Usage notes

• The selected feature layer must be hosted by ArcGIS Velocity, be an ArcGIS Online hosted feature layer, or an ArcGIS Server feature layer.
• The schema of the incoming data and the destination feature layer must generally match. Each should have the same geometry type, spatial reference, and the fields present in the incoming data should exist in the destination feature layer. Differences can include the following:
  • The destination feature layer can have additional fields not present in the incoming data that may be used for data enrichment.
  • The Map Fields tool can be used to transform the schema of the incoming data in an analytic workflow to align with the schema of the output feature layer.
• ArcGIS Server feature layers must be referenced in an ArcGIS Online portal item ID. To do this, go to your ArcGIS Online content page, and add an item referencing the layer by URL. If applicable, store credentials with this ArcGIS Online item. Then, ArcGIS Velocity feature layer existing output can be specified to point to this ArcGIS Online portal item ID that points to the ArcGIS Server feature layer URL.
• For ArcGIS Velocity layers, a data retention policy is required for all output feature layers since data will grow over time. When writing to an existing feature layer and choosing the Add new features option for the Data storage method parameter, the selected feature layer must have a data retention policy set to something other than No purge. For more information, see Introduction to data retention.
• When editor tracking is enabled and the Data storage method parameter is set to Add new features, the creator and editor user and date will always be the same. If the Data storage method parameter is set to Keep latest feature, a track observation that is updated will only have the editor user and date updated after the first observation.

Parameters

Parameter	Description	Data type
Feature Service Portal Item ID	The Portal Item ID of the corresponding feature layer item created in ArcGIS Online. The feature layer must belong to the user creating the analytic.	String
Data storage method	Controls whether all new features are added to the layer or whether existing features are updated. Options include the following: Add new features—All new features will be added to the feature layer. Keep latest feature—Only the latest feature for each unique Track ID will be kept. The output data schema should have a Track ID and Start Time key fields identified.	Boolean
Creator or editor username	Specifies the user name to use as the creator or editor for processed data. The user name can be derived from a field of the incoming data or set as the user name of the analytic owner. The Creator or editor username parameter only applies and is shown when the existing feature layer already has editor tracking enabled. For more information, see the Usage notes above.	String

Considerations and limitations

• The selected feature layer must be hosted by ArcGIS Velocity, be an ArcGIS Online hosted feature layer, or an ArcGIS Server feature layer.
• Restrictions exist on the number of records written to ArcGIS Online hosted feature layer outputs using the Feature layer (existing) output, including:
  • Real-time analytic output:
    • When writing to an ArcGIS Online existing hosted feature layer from Velocity real-time analytics, no more than 120 events per minute can be written.
  • Runs once big data analytic output:
    • Up to 50,000 records can be written to an ArcGIS Online existing hosted feature layer output.
    • The hosted feature layer must support the append function when writing from a runs once big data analytic
  • Scheduled/recurring big data analytic output:
    • The number of records that can be written to an ArcGIS Online hosted feature layer output depends on the run frequency of the analytic. For each minute between each run, 120 records can be written per minute. For example, an analytic that runs every minute can write 120 output features per run, an analytic that runs every 5 minutes can write 600 output features per run, and an analytic that runs every 30 minutes can write 3,600 output features per run.
  • ArcGIS Online organizations that have the premium data store can write at a higher rate depending on the premium data store plan. For more information on the premium data store, see Premium Feature Data Store.