Orphaned Blocks

[VahanN95]

Hello,

I am pretty new in this topic and have a question.
Lets say we have have 3 miners M1 M2 M3. And 5 transactions T1 T2 T3 T4 T5.
And lets assume that

M1 -> T1, T2, T3
M2  -> T2, T4
M3 -> T1, T4, T5

And M1 mined successfully and added new block to the chain. But on the other hand M2 and M3 mined their blocks as well.
So the question is what will happen with other transactions of Orphaned blocks and how they will be retried?
And Second question. After M1 broadcasted its block T1, T2, T3 will exists in the block chain. How the system will make sure that these transactions will not be reused?

[cromewar]

Hello @VahanN95

what will happen with other transactions of Orphaned blocks and how they will be retried

This is due to the confirmations on the blockchain, let me go in deep into it.

1. Each node has a copy of the blockchain, so the nodes are competing with each other to be the ones to register the transaction... when a node wins that competition the rest of the nodes works as confirmations, making sure the block the node is trying to register is the same as them, at the end the Sakamoto consensus uses the largest chain which has 51% coincidence as reference

How the system will make sure that these transactions will not be reused?

2. After a block is written there are more confirmation, which are block confirmations, basically means more blocks are added after the block on where your transaction was registered, if there is more blocks it means that the blockchain is correct and the transactions were permanently added as immutable of the blockchain, meaning the cannot be reused.

[VahanN95]

So dose that means that per every block all the transactions are checked if it is existing or not?
So in the example I have mentioned M2 and M3 have some transactions which will be in the blockchain but some other are not. So Ho the miners are understanding what transactions are pending?

[cromewar]

This happens automatically using math, basically the first to solve the problem to register the transaction is the one who proposes that register/block, if other nodes gets to the same result and confirm the transaction is legit it the transaction/block get written permanently. The don't "know" if the others are pending or not, they just try to make the register, but if the register was already proposed they are used just as confirmations.

[VahanN95]

Thank yo so much!