Quote from: M Calvin Ayre=https://twitter.com/CalvinAyre/status/1119692170947112960

Steve Shadders is head and shoulders the top expert in the world in block chain scaling. Meet him in person at CoinGeek Scaling conference end of May in Toronto:

See all this from the Original source https://www.yours.org/content/on-forks--orphans-and-reorgs-0c0c39d3c79b
From Mr Shadders, BSV's Technical Director:

On forks, orphans and reorgs

TLDR;
Security of a forked chain is near identical to an unforked chain.
No transactions were lost or double spent.
Reorgs are part of the Bitcoin design and incentivize more secure 0-conf.
The design turns the unreliability of distributed systems from a problem into a feature.

https://imgur.com/download/stWqtjk

Background
On 18th April 2019 we saw an interesting event on the Bitcoin SV block chain. Two sets of miners began mining competing chains which resulted in two chain re-orgs. The headline number on twitter is that there was a re-org of 3 blocks then a second re-org of 6 blocks. What hasnt been pointed out is that the 6 block re-org encapsulated the 3-block reorg so from an outsiders point of view it was like part of the chain switched to a longer branch then switched back to the original branch once it became longer. Imagine a race where someone takes the lead then falls back into second place again.
The headline number I havent seen reported yet is that during the event no chain was ever more than 2 blocks ahead of the other. Perhaps more importantly we have seen very little discussion on how this affects users.
Bitmex has published some useful data that helps us to unpick this event here: https://twitter.com/BitMEXResearch/status/1119197415804932096?s=09
They also make the comment:
Based on the current most work Bitcoin Cash SV chain, all the TXIDs (except coinbase transactions) from the fork made it the main chain. Therefore no double spends appear to have occurred
What is a re-org?
Put simply, it is a normal part of the Nakamoto consensus. It is first important to clarify the terminology. A re-org is an event, and an orphan block (or chain) is the consequence of that event. In a 2014 report CEX.io noted that on the BTC blockchain orphans occurred 1-3 time a day: https://blog.cex.io/bitcoin-dictionary/what-is-an-orphan-block-9632
These are almost all 1 block re-orgs. Blockchain.com appears to have been collecting this data between 2014-2017: https://www.blockchain.com/charts/n-orphaned-blocks?timespan=all&daysAverageString=1&scale=0
When two miners find a block at near the same time the network divides into two sets of miners mining on top of different blocks. This usually resolves when the next block is found. One of the competing blocks is retained as it now part of a longer chain and one is orphaned. Occasionally both second blocks will be found near the same time and the race continues this time with 2 blocks potentially orphaned once its resolved by the mining of a third block.
This can be exacerbated by slow block propagation. We noted earlier miners find a block at near the same time. What really matters is not the time miner finds the block but the time the other miners see the block. Theyll start mining on top of the one they see and validate first. Since miners are highly incentivised not to have their blocks orphaned (theyll lose their block reward if that happens) they are also highly incentivised to propagate their blocks quickly.

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To read the rest of this report and discover the solutions, go to https://www.yours.org/content/on-forks--orphans-and-reorgs-0c0c39d3c79b