If you can specify what RDBMS you are using that would also aid in providing a more accurate answer. If it is Microsoft SQL Server, then data owners, must have a schema that is the same name as the user (data owner). The data owner should be a "head-less" account (e.g. planning, dpw, etc..). Editors and Viewers can be either database or OS/external authenticated and would not own any data and thus just require access to the schema for any data manipulation language (DML) they may be doing. The data owner would grant permission to just view (select) or edit (insert, update, delete) to the editors and viewers through ArcCatalog. Roles can also be used to group the users, and the permissions could be granted to roles through ArcCatalog. More information is available in the help at the following location: http://help.arcgis.com/en/arcgisserver/10.0/help/arcgis_server_dotnet_help/index.html#/What_are_user_accounts/002q00000027000000/
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