Replacement System from ITS Provides Business Continuity for VAX-Based System
Industrial Technology Systems Ltd (ITS) has won a contract to replace Sellafield Ltd’s obsolete Swarf Inventory Monitor (SIM) Computer System, removing the reliance on a single inventory computer.
The primary requirement for the project, based in the two Fuel Handling Plant (FHP) decanner cells in the Magnox Encapsulation Plant (MEP), was to replace a single outdated MicroVAX II computer running VMS with a suitable emulator, without changing the applications or the interfaces to the external systems and thereby avoiding costly revalidation.
A secondary requirement of the project was the enhancement of the mission critical system so that the two processing plant areas (caves) were not reliant on a single applications platform. Additional file handling management was also required to allow the retransmission of data files on request to higher level systems.
In normal operation, the original system was capable of functioning with either one or both of the processing plant areas in operation. In the replacement system the core functionality of the applications is provided in two identical VAX emulator systems, with the plant level interfaces from the independent processing plants connected to the associated emulator via an existing patch panel.
If required, the plant level signals from both processing plants can be patched into a single emulator, which can then service both areas in the same way as the original single platform system.
The output of the resultant data files are transferred to a third VAX emulator which functions as a data buffer and file administrator, storing, logging and forwarding the received data files to the higher level systems. The buffer computer assumed the network identity of the original VAX, which makes the whole replacement transparent to the higher systems.
One challenge facing ITS’ project team was the provision of sufficient serial ports on the replacement servers to match those on the original VAX, which had 16 ports connected to plant interfaces and dumb video terminals. This was achieved by inserting PCI cards with 16 serial ports on flying leads. The virtual VAX ports (TXA0: to TXA7: and TXB0: to TXB7:) were mapped to the physical com ports via a Charon-VAX configuration file, which specifies the hardware devices from the original system that are to be emulated in the CharonVAX application.
The replacement system excelled its original requirements for increased resilience and file management functionality, by providing significant performance-related benefits associated with greatly reduced system start-up and shutdown times and backup procedures, thereby increasing the system’s available up-time.
The start-up and shutdown of the system can be achieved in less than three minutes; the original system took more than 20 minutes. Similarly it takes less than ten minutes for the backup procedure, requiring the VAX emulator to be shutdown to allow a copy of the container file to be made for subsequent transfer to DVD before restarting the emulator. The previous backup procedure on the original Micro VAX took several hours, using a standalone backup utility for transferring the image of the system disk to magnetic tape.
The replacement system successfully completed extensive Client Acceptance Tests at the ITS offices, before being transferred to site for additional site integration trials prior to installation on plant.
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