Hy! We'd like to solve a follow issue. There must be two main data store for perfect performance. One of them contains only spatial data as a one column data and the otherone has the attributes as a table without any spatial information. It is needed to be published as a service to Portal for ArcGIS and must be editable by the clients. The main question is that is is possible in any way or we shouldn't try that? We would be very thankful for any help.
So there are two approaches to publishing a feature service, neither of which seems like you'll be able to accomplish in your current architecture. If you were going the route of a hosted feature service in Portal, the data would be copied from your original source location into the ArcGIS Data Store registered to the hosting server. It then wouldn't be referenced from the original location, (and this is assuming that there wouldn't be a problem copying the data from two separate tables). Another approach is to publish a traditional map service with feature access, but that requires that the data reside in the same workspace.
Unfortunately, the first requirement for a feature service is that the data is in the same workspace. You may need to rethink the architecture of the databases if you want feature access.