Hyperledger network roles assigned to peer nodes

Question

Hyperledger assigns network roles based on node type and transaction execution is separated from transaction ordering and commitment. I read somewhere that 'Executing transactions prior to ordering them enables each peer node to process multiple transactions simultaneously'

I want to understand how how one can execute a transaction prior to ordering one?

Answer 1

In a hyperledger fabric network transactions are initiated with client applications sending transaction proposals to endorsing peers. 

Each endorsing peer simulates the proposed transaction, without updating the ledger. The endorsing peers will capture the set of Read and Written data which are called R-W Sets.

The application then submits the endorsed transaction and the R-W sets to the ordering service. 

The ordering service takes the endorsed transactions and RW sets, orders this information into a block, and delivers the block to all peer nodes.

The committing peers validate the transaction by checking to make sure that the R-W sets still match the current world state.

Committing peers are responsible for adding transaction blocks to the shared ledger and updating the world state.