Once an external content type is created then they can be used in Microsoft SharePoint® solutions to expose the data from external systems using External Lists, external data columns and Business Data Web Parts. However, unlike solutions that are based on data stored internally in lists and libraries, when exposing external data using Business Connectivity Services (BCS), there are at least three levels of authorization plus BCS external system throttling thresholds in use:
- SharePoint permissions. Allows a user access to the site, external list, the list that contains the external column and pages where Business Data Web Parts are used.
- Business Data Connectivity (BDC) objects. External content types could be used extensively in your SharePoint installation, and solutions built using them could be a critical to your business. A modification to an external content type could stop those solutions working as designed; therefore, external content types can be guarded against accidental or malicious modifications. For example, even if a user has SharePoint permissions to view an external list, if they do not have permissions on the external content type, no data in that external list will be displayed.
- External System authorization. Most external systems have their own authorization settings determining who can see the data as well as who can view, create, manipulate, or delete the data.
- BCS threshold limits. These limits are enabled by default to prevent denial of service (DoS) attacks. A user may have the correct SharePoint, BCS object and external system permissions, however, if the number of items returned from the external system exceeds the threshold limits, data will either not be displayed or only a subset of the data will be displayed.
Using the browser or Microsoft Office applications, it is not always obvious as to which authentication settings or throttling threshold is preventing the user from seeing the data. This series of blog posts looks at the errors users may see when a page should be displaying data from an external system.
The other parts of this blog post are:
- Threshold Limit Errors (external system throttling)
- Changing External System Throttling
- External Content Type Authorization Errors
- External System Authorization Errors (to be written)
- Summary (to be written)
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