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See the Microsoft SQL Server section information about SSRS requirements.
Staring from Since version 4.2 Web Workbench now has a Report Server Local Mode that removes has been introduced to remove the need for SSRS to render web reports. With this mode turned on, the web application renders the reports locally with Microsoft ReportViewer Controls. However it may be significantly slower than SSRS. For Therefore SSRS is still recommended for on-premise installations, SSRS is still recommended.
Workbench MDE Version
Web Workbench requires Workbench MDE version of at least 7.41.3.0.
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