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HP OpenVMS Systemsask the wizard |
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The Question is: I have a DMA device feeding data into the ALPHA at 30 MBytes per sec. non-stop. I must transfer that data to a RAID system before more data comes in to overwrite what I have. Currently I use 8 rotating input buffers of 10 MBytes each and use QIO with AST routines. I can write about 15GBytes of data before I somehow get interrupted and lose a few miliseconds worth of data. I am running at priority 63. What techniques can I us e to keep from getting interrupted, or find out what is doing it? The Alpha is completely dedicated to this process and I have complete control over what runs on it and when. When I set up the system using hand-shaking, I can sustain data rates of 63 MB ytes per second without losing data so I know my RAID system and VMS are running fast enough. But when I remove hand-shaking (which will be the real-world case) I sometimes lose those chunks of data. The Answer is : Please contact the customer support center, as this could arise from anything ranging from a hardware error to a software problem -- many potential sources of interruptions exist -- and thus details on the RAID system and the particular Alpha will be of interest, as will details on the incoming data path and the RAID data path will be of interest. Details on exactly what you mean by hand-shaking will also be of interest -- there are many different hand-shaking protocols. The OpenVMS Wizard will assume you have ruled out an error within the incoming data stream. The OpenVMS Wizard will also assume you are using 64-bit addressing. Processes using 32-bit addressing are limited to one (P0) to two (P0 and P1) gigabytes of address space. Fast I/O may also be of interest, and current or expected V7.3-2 Fast Path features (depending on the RAID device) if this is an SMP configuration. The OpenVMS Wizard will further assume you have all current ECO kits installed for this configuration. For information on synchronization bugs and related coding errors, please see topic (1661) -- high loads can uncover latent bugs in application code and even in OpenVMS itself. (In the experience of the OpenVMS Wizard, the former case is more common than the latter.) Again, please contact the support center or services organization, as a far more detailed investigation will be required here.
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