We propose SSketch, a novel automated framework for efficient analysis of dynamic big data with dense (non-sparse) correlation matrices on reconfigurable platforms. SSketch targets streaming applications where each data sample can be processed only once and storage is severely limited. Our framework adaptively learns from the stream of input data and updates a corresponding ensemble of lower-dimensional data structures, a.k.a., a sketch matrix. A new sketching methodology is introduced that tailors the problem of transforming the big data with dense correlations to an ensemble of lower-dimensional subspaces such that it is suitable for hardware-based acceleration performed by reconfigurable hardware. The new method is scalable, while it significantly reduces costly memory interactions and enhances matrix computation performance by leveraging coarse-grained parallelism existing in the dataset. SSketch provides an automated optimization methodology for creating the most accurate data sketch for a given set of user-defined constraints, including runtime and power as well as platform constraints such as memory. To facilitate automation, SSketch takes advantage of a Hardware/Software (HW/SW) co-design approach: It provides an Application Programming Interface that can be customized for rapid prototyping of an arbitrary matrix-based data analysis algorithm. Proof-of-concept evaluations on a variety of visual datasets with more than 11 million non-zeros demonstrate up to a 200-fold speedup on our hardware-accelerated realization of SSketch compared to a software-based deployment on a general-purpose processor.