In Screen Scraping, ABAP Dynpro screens are used as data sources. Note the following constraints when using Screen Scraping data sources:
There should be at least one Query (Search Help) and one Read operation in a Data Model.
The more dynamic a screen is, the less stable will be any SAP Gateway service generated from Data Models based on such Screen Scraping data sources.
Make sure that the transaction you record behaves consistently for the possible input values. Where you are aware that a transaction recorded in Screen Scraping can behave differently at runtime, then the generated service will fail.
The following screen elements are not supported by Screen Scraping:
All EnjoySAP controls, that is ActiveX controls such as ALV, Tree, HTML, Picture, text editor, and many more.
ABAP lists, typically generated in reports and selection pop-ups.
Search helps are used by Screen Scraping as data source provider for query operations.
The search help definitions are retrieved from the ABAP Dictionary.
A constraint for this approach is that, it cannot support search helps that are provided locally in the screen (using ON VALUE REQUEST command). It only supports search helps that are defined in transaction SE11.
Table controls can be used only with the Read operation. Currently it is not possible to Update, Create, and Delete table entries.
Screen Scraping uses the paging control (page down button) in order to scroll through tables and retrieve all their entries. If no page down button is provided in the screen, only the first rows which are visible in the screen can be retrieved.
See also the constraints for SAP Gateway in the SAP Note number, 1574568