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If you have the source service definition attached to the service, you will be able to clone both. This is because this attachment lets your ArcGIS Organization know you have the appropriate permissions to perform operations on can access both the RMS Map Service and its data source, and it is able to inform BMO that you have those permissionsto pass the necessary information on to BMO. In this situation, the item in the new ArcGIS Organization will be a Hosted Map Service.
Note: If the source is missing in the above operation, BMO will restore the Map Service as a Registered Map Service and point back to the original data source specified in the source Organization.
Think of it like this - your ArcGIS Organization is an encyclopedia. The Registered Map Service is an entry in the encyclopedia that cites a table. That citation could point to a table in another publication altogether (different encyclopedia, scientific journal, etc.), or it could point to a table in the appendix of the encyclopedia. In the second case, the table is "attached" to the entry because they are in the same book. This is analogous to when a source service definition is attached to a RMS.
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