Thank you. Sent from my iPhone
> On May 21, 2021, at 7:39 PM, Mike Schwab <[email protected]> wrote: > > Async mirroring would be possible. The bad / good thing is your > source dasd track could be updated several times between passes. What > the controller does is look at the updated track table, 1 bit per > track, copies the tracks in order, resetting the bits when read and > acknowledged, then proceeds to the next track. When it gets all those > tracks copied, it reads the updated track table for the next pass. > > If you process the updated tracks fast enough, the number of tracks to > send drops with each pass until updates are sent almost immediately. > If you process the updated tracks too slow, then the number of tracks > to send keeps growing. > > The key is the transmission rate to the endpoint. I think the last > time I heard the limit was continent wide, because the links between > continents simply didn't have enough throughput capacity to get the > secondary up to speed. Even with the land bridge, N/S America is > pretty slow, and African links too, despite cables across the > Mediteranian. Maybe Europe / Asian would not be too bad. Antarctica > is satellite only. > > Australia is a long separation. I had a friend in Australia who kept > getting notifications that her password was changed in Shanghai China, > so she changed it, got the message again, and repeated a few times. I > pointed out that that was probably where the Australian underwater > cable came ashore and the location registered, because the date time > of the change was when she changed her password. > > https://www.submarinecablemap.com/ > >> On Fri, May 21, 2021 at 2:34 PM Cameron Conacher <[email protected]> wrote: >> >> Hello folks, >> I am trying to find out what we could consider to be a "safe" maximum >> distance for mirroring DASD from one site to another. >> We have a situation where site #1 will be thousands (9,000) of miles away >> from site #2 (across the ocean. >> >> I realize there would be a great deal of latency involved. >> But is this even possible or is it simply a non-starter? >> >> The second question I have is, suppose that I waved a magic wand and >> suddenly all my data was sitting comfortably in site #2. >> Could I (again ignoring latency for the moment) run a batch JOB or CICS >> transactions in site #1 that accessed the data 9,000 miles away in site #2? >> My thought here was if the data must absolutely be relocated, and >> people are willing to accept there will be latency, can we just access the >> DASD at site #2, rather than building a large data centre and performing >> all of the processing in site #2? >> Even if we run the processing at site #2, there will be many interfaces >> between site #1 and site #2. >> >> I know there are hard distance limitations. >> I think Global Mirror is limited to about 1500 miles. >> And I would hazard a guess that remote DASD would not be viable either. >> >> But I wanted to see if someone really "knows", rather than something I may >> have mis-remembered. >> >> Any thoughts/opinions are appreciated. >> >> Thanks >> >> ---------------------------------------------------------------------- >> For IBM-MAIN subscribe / signoff / archive access instructions, >> send email to [email protected] with the message: INFO IBM-MAIN > > > > -- > Mike A Schwab, Springfield IL USA > Where do Forest Rangers go to get away from it all? > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
