BlockChain: Always get a new Hash I am asking a simple question. Why we say that we would always get a new hash in a blockchain? Why we can't have collisions?

One way of collision is that the hard disk becomes full and there is no more space to store a transaction.

Some body please guide me.

Zulfi.
Blockchain uses a cryptographic hash function that is designed to have collision resistance.  Thus, while it's possible you might run into a pair of inputs that produce the same output... it's very very unlikely to happen by chance; and it is believed to be very difficult to intentionally find such a pair of inputs.

Disk space has nothing to do with collisions in the hash function.