Any piece of data cannot be retrospectively changed in a blockchain. Just this capability makes blockchain one of the most secure technologies when it comes to the data immutability. Every user can see the whole history of all transactions in a blockchain. The consensus procedure enabled by the very code of blockchain provides an unmistakable verification of each block.
The error-free tracking of everything happening in a blockchain is conducted in a real time mode. The cryptographically protected blocks are added to a blockchain one by one. Every action is absolutely transparent since the decentralized nature of blockchain eliminates any forgery.