Mainframe Migration - 6
on the mainframe and non-mainframe systems represents a good apples-to-apples comparison of the platforms. These ratios have been born out in customer workloads that have undergone migration from a mainframe.
Mainframe Migration Architecture
The architecture of the Micro Focus Enterprise Server with the Mainframe Transaction Option works well with the Windows Server 2003, Datacenter Edition to distribute transactions effectively across all available processors. This is important for the system to scale accordingly as more processors were added to the system during the scalability tests.
Fig.1. Enterprise Server with Mainframe Transaction Option process structure
The Single Execution Processes (SEPs) host a runtime CICS environment for a single transaction. The SEPs use process boundaries in Windows to provide the same fencing of memory resources as storage keys and protected instructions do in the System/390 architecture for mainframe CICS. Together, the SEPs form the traditional “CICS Region” for the transaction system and are managed as a group by the Directory Server (MFDS). The Communication Servers (MFCS) provide network input/output control to users. All components are linked through a shared memory space. The shared memory component provides terminal input/output areas (TIO, transaction COMM areas and other shared CICS structures. Although each application environment will vary, the scalability tests found that a ratio of 3.75 to 4.5 SEPs to physical CPUs in the partition is ideal for handling TPC-C workload. The scalability tests found that a larger number of SEPs increased Windows kernel execution time, primarily in increased context switching between processes. A lower SEP:CPU ratio resulted in starvation of CPUs and a lower attainable CPU utilization rate.
The numbers of users and the transaction rates scaled accordingly as the number of processors were increased during these tests. At its peak, 5160 user terminal sessions were simulated requiring a shared memory allocation of 1 GB and 2 MFCSs. Transaction environments that have different characteristics would likely be tuned differently. For example, long running transactions (“batch” jobs in the extreme) would require increased numbers of SEPs. Transactions that had a higher
WinHEC 2005 Version - April 20, 2005