  Many existing blockchains do not adequately address all the characteristics
of distributed system applications and suffer from serious architectural
limitations resulting in performance and confidentiality issues. While recent
permissioned blockchain systems, have tried to overcome these limitations,
their focus has mainly been on workloads with no-contention, i.e., no
conflicting transactions. In this paper, we introduce OXII, a new paradigm for
permissioned blockchains to support distributed applications that execute
concurrently. OXII is designed for workloads with (different degrees of)
contention. We then present ParBlockchain, a permissioned blockchain designed
specifically in the OXII paradigm. The evaluation of ParBlockchain using a
series of benchmarks reveals that its performance in workloads with any degree
of contention is better than the state of the art permissioned blockchain
systems.
