Below u'll find a description how Qubic handles and distributes data of the ledger. Unlike Bitcoin, Qubic doesn't use a blockchain, so it doesn't need to store all transaction nor to prune some data:


Consistency of the ledger

All interactions between Qubic providers are non-deterministic. When a provider shares information about a transaction it sends the data to randomly chosen peers. This can lead to a situation when some providers don't see some transactions and hence don't destroy/create qubics. Unreliability of UDP, which is used to transfer data, makes the situation even worse, because some providers don't receive data, although transactions were sent to them. Obviously, the Qubic network must have a way to reach consistency at some point, otherwise differences between copies of the ledger will accumulate, leading to a collapse of the whole system.

Consistency is kept on a periodic basis. This synchronization process is a part of the bootstrapping process, because in the worst case scenario a provider has to download all data just like it's a brand new provider.

Once a day (at 00:00:00 UTC) every provider makes a copy of the ledger and calculates its root hash. This hash lets to compare all existing qubics using a 256-bit number, if there is a difference even in a small piece of two copies of the ledger then these hashes will be different. Every provider asks the others for the root hash and compares its hash to the hash of the quorum, and if there are any differences it requests data necessary to build identical ledger. If a provider is bootstrapped then it downloads entire set of qubics.

It should be noted that the ledger can contain billions of qubics, so the synchronization process can take a lot of time. During this time the provider keeps processing new transactions, working with the original ledger which is changed in real-time.

The synchronization relaxes requirements to Qubic providers. It's not necessary to have a high uptime percentage, a provider can be shut down for a maintenance without serious consequences.

Read more: http://qubic.boards.net/thread/18/consistency-ledger