Content-based page sharing (de-duplication) is a heavily used technique to improve memory efficiency in virtualized systems by identifying and merging identical pages. For many years now, the Linux kernel has offered this de-duplication technique via the Kernel Samepage Merging (KSM) feature. Although KSM in general works well, it is not used in multi-tenant database systems even though multiple tenants often manage similar data. One reason is that pages must be binary identical, which is a severe restriction. Secondly, KSM is seemingly scheduled as a single-threaded process by the OS, independently of the database workload, which further limits its applicability for in-memory systems with terabytes of main memory. To overcome that, we propose an extended de-duplication mechanism called De²Dup for memory-centric multi-tenant database engines. De²Dup extends de-duplication with a delta mechanism to significantly boost the application, especially when pages are not binary identical. Moreover, our De²Dup mechanism allows to steer the search for duplicates and has low overhead as we are able to offload the complete execution to a modern on-chip accelerator for memory operations in an asynchronous manner on recent Intel server processors. In addition, De²Dup offers an efficient way for on-the-fly tenant-aware data reconstruction during scan operations.