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DataDirect Shadow Advanced Scalability and Load Balancing
In truth, most application developers do not want to know what is taking place on the mainframe when they request data or re-use a legacy application. Shadow Advanced Scalability transparently balances workloads and increase connection resource on the mainframe for enhanced scalability.
Transparent Load Balancing through Shadow
From an application developer's perspective, mainframe integration is provided through a single Shadow Server instance that is defined to the application. Behind the scenes, application requests are serviced by one of several Shadow Server instances as each request is automatically routed to the Shadow instance with the greatest available resources.
- The Shadow Advanced Scalability option consists of two major components:
- Load balancing component - transparently distributes work across multiple Shadow address spaces on the mainframe and provides support for IBM's WLM feature
- Virtual Connection Facility (VCF) - increases the total number of possible client connections
Together, these components significantly increase the number of concurrent users and reduce the possibility of application failures. When Shadow Advanced Scalability is implemented, Shadow Server instances are automatically deployed on the z/OS images with the greatest available resources. This feature extends the mainframe's native load balancing capabilities to Shadow and the distributed applications that use Shadow.
- Load balancing key features:
- Dynamic load balancing between multiple Shadow Servers
- Support for IBM Workload Manager
- Load balancing key benefits:
- Improved application availability and performance
- Support for virtually unlimited concurrent users and transaction rates
Virtual Connection Facility
The VCF component of Shadow Advanced Scalability significantly increases the number of client connections possible. When a client is active, it uses a standard "real" connection to z/OS. When a client is idle, the VCF option switches the client to a "virtual" connection. All shifts from "real" to "virtual" connections and back are transparent to the client and never interrupt a logical unit of work. The Shadow VCF never switches from "virtual" mode to "real" mode until requests are ready for execution.
On the mainframe, the Shadow VCF maintains a thread pool that is accessible to all active clients. When a client is idle, the thread is dropped. Use of thread pooling eliminates the overhead and time required for z/OS thread creation, database creation and security checking. The thread pool automatically shrinks and expands based on activity levels to provide the optimum balance of performance and resource usage.
- Virtual Connection Facility key features:
- Mainframe connection pooling complements connection pooling implemented by the distributed application
- Dynamic thread activation based on application workload
- Virtual Connection Facility key benefits:
- Improved application availability and performance
- Decreased mainframe CPU utilization
- Support for virtually unlimited concurrent users and transaction rates
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