HPE NonStop Pathway is an application framework that is a mainstay of mission-critical OLTP systems. It supports a requester (client) – server model, and delivers application scalability by distributing requester workloads across dynamic pools of application server processes (serverclasses) that in turn are spread across multiple HPE NonStop server CPUs. It also offers high levels of application availability by monitoring and automatically restarting server processes in the event of failure.
The Pathway model delivers excellent application availability for a single HPE NonStop server, providing local fault tolerance. However, this model still necessitates application outages for certain planned system maintenance activities, and it offers no protection against unplanned system outages. These limitations are addressed by Pathway domains (PDs), which allow the serverclasses to be distributed across multiple NonStop server systems. This capability improves application scalability and availability, protecting against some server failures. However, even though application availability is improved by PDs, if the database being used by those applications becomes unavailable, then the application is still down.
The combination of HPE Shadowbase data replication and PDs across nodes offers a powerful business continuity architecture to meet the requirements of continuous application and data availability. Working together, they provide geographically dispersed application and database services. The data is made available on other nodes by Shadowbase data replication, and the application services are made available on other nodes by PDs. When a node outage occurs (for whatever reason), PDs automatically detects it and switches all user request traffic to the surviving node(s). They can continue processing because the data on those nodes has been synchronized with the failed node by Shadowbase data replication. Thus, all the necessary components (applications and data) are in place to maintain business services with minimal downtime. In summary, PDs and Shadowbase data replication are perfect for each other – together they provide scalability and protection from any single failure for both your application services as well as your application database.