Is it possible to update tiles in a Tile Service hosted on ArcGIS Online?

Answer

Yes, it is possible to update tiles in a Tile Service hosted on ArcGIS Online. A new Hosted Tile Service can be published with the updated tiles and then existing web maps that use the original Tile Service must be updated to the new service. However, in some cases users may want to update an existing Hosted Tile Service without having to republish the entire dataset or having to replace services in existing web maps. This can be accomplished with the workflows described below.

Tiles in an existing Hosted Tile Service can be updated using one of the following methods:

Method 1:
Overwrite the existing Tile Service through publishing a map in ArcMap using Share As > Service. When overwriting a service, the existing map tile item is deleted from ArcGIS Online and a new item is created with the same name. The new item is created in the root folder and the item is assigned a new ID. Sharing must be reconfigure and, if necessary, move the item back to the folder it was in before republishing.

Methods 2 and 3 discuss updating the tiles in the existing Tile Service, rather than republishing all the tiles.

Note: 
This workflow requires that an accompanying Tile Package or Service Definition to be present with the Tile Service in My Content. 

1. Open a working map document that the Tile Service was originally published from and sign in to ArcGIS Online, if necessary.
2. From File, navigate to Share As > Service.
3. Select to Overwrite an existing service, then select the name of the Tile Service to overwrite. Change any of the existing parameters in the Service Editor as needed and select Publish.

Note: 
This method consumes credits when performing the overwrite as the updated tiles are generated in ArcGIS Online. 

Method 2:
Update the existing Tile Service through ArcMap using the Manage Map Server Cache Tiles tool. This tool can be used to create new tiles, replace missing tiles, overwrite outdated tiles, and delete tiles.

Note: 
This workflow requires that the original Tile Service have been created through publishing a Hosted Feature Service in My Content. This workflow is not expected to update tiles when the Tile Service has been published directly from ArcMap or published from a Tile Package.

1. Open a working map document that the tile service was originally published from and sign in to ArcGIS Online, if necessary.
2. In the Catalog window, expand My Hosted Services (Organization Name).
3. Right-click the tile service > Manage Cache > Manage Tiles.
4. Define the parameters in the Manage Map Server Cache tiles dialog box.
   
   Particular scale levels or an area of interest can be defined to limit the update extent. In this workflow, the current scale of the data frame when defining the area of interest may affect the appearance of the tile service. Consider working with the scale levels used by ArcGIS Online to maintain consistency when updating from ArcMap. Refer to ArcGIS Help: Designing a map to overlay ArcGIS Online, Google Maps, or Bing Maps for more information.

Note: 
This method consumes credits when performing the update as the updated tiles are generated in ArcGIS Online.

Method 3:
Create and use a tile package to update particular levels of display using the REST endpoint of the Hosted Tile Service and the Import Tiles operation.

1. In ArcMap, use a desired workflow to create a Tile Package which contains the Levels of Interest that include the updated tiles.
2. Add the Tile package as an item to My Content in ArcGIS Online without publishing the package to a service.
3. Browse to the Item Details of the Tile Package and copy the Item ID from the URL to be used as a parameter.
4. Browse to the REST page of the original Tile Service to be updated from the Item Details page.
5. In the URL of the Tile Service REST page, type admin after rest. For example:

http://tiles.arcgis.com/tiles/Wl7Y1m92PbjtJs5n/arcgis/rest/admin/services/Tiles/MapServer?token=<your token>

Users may be prompted to log in again with ArcGIS Online credentials.

5. At the bottom of the page, click Import Tiles.
6. Enter the Item ID of the uploaded Tile Package for the Source Item ID parameter. This is the only required parameter but additional parameters such as Extent and Levels can be entered to limit the area of the tiles that is updated. Refer to ArcGIS Online: Import Tiles for more information.
7. Click Import Tiles to begin the update.
8. In the Admin view of the service, scroll to the bottom and select Jobs. Check the status of the job submitted and refresh until it displays DONE.

Note:  
This method does not consume credits as the new tiles are generated in ArcMap when the Tile Package is created.