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Ongoing changes in industrial automation aim to-wards a flat and highly interconnected architecture that includes end-to-end real-time enabled machine-to-machine communications. Several technologies, such as OPC Unified Architecture (OPC UA) publish-subscribe and time-sensitive networking (TSN), facilitate that change. While OPC UA PubSub and TSN can already provide real-time capabilities, the parallel operation with standard OPC UA client-server remains an open challenge. This article presents preliminary results for solving concurrent information model access between OPC UA PubSub and client-server. The results include the overall RT-TSN-OPC UA concept, an analysis of common concurrent data access mechanisms for their suitability, and identifying critical code segments in the open62541 OPC UA stack. The paper concludes by outlining further research focusing on implementing and evaluating a wait-and obstruction-free mechanism into open62541.