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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
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Virginia, Chris, Robert, > It shows up as "latency" on the NWS website, however, I believe the real > problem is duplicate data being re-downloaded as the TGP48/49 server (w/ > 2GB queue) switches primary/alternate between the two sources (RDS and TDS > w/ 4GB queues). LDM seems to start up a new connection when switching > sources and data that has aged out of the smaller downstream queue is > re-downloaded from the larger upstream queue. The duplicate data appears as > a false latency. Please correct me if I'm wrong as most of my LDM knowledge > if from trial and error....mostly error. I suspect the large "latencies" you're seeing are due to the size of the product-queue being incompatible with the maximum allowed latency parameter, which is 1 hour by default. If the product-queue is too small to hold more than 30 minutes worth of data, then a duplicate data-product that arrives 45 minutes late will be accepted as a new data-product because its previous arrival has been purged from the product-queue. Beginning with LDM version 6.9, the LDM system can now automatically reconcile the size of the product-queue and the maximum latency parameter, either by increasing the size of the queue, decreasing the maximum latency parameter, or notifying the LDM user via email -- depending on the value of the "reconciliation-mode" parameter. You should be able to find a lot of support-email on this subject <http://www.unidata.ucar.edu/software/ldm/#help> by searching for "reconciliation-mode". Also, this feature is documented in the online LDM reference <http://www.unidata.ucar.edu/software/ldm/ldm-6.10.1/basics/index.html>. > I know there is a flag in LDM to limit the downloading of data to that > below a certain latency threshold, however, you risk missing data from a > site that is experiencing actual latency (I've seen individual sites with > real latency over 3000 seconds due to telco problems). > > -- > Chris Calvert > Software Engineer > National Weather Service > WSR-88D Radar Operations Center > 1313 Halley Circle, Norman, OK 73069 > (405) 573-3323 Regards, Steve Emmerson Ticket Details =================== Ticket ID: QYR-744357 Department: Support LDM Priority: Normal Status: Closed