Off-the-chain data

There are multiple scenarios where data cannot be stored on a chain:

• State variables: Data stored on an Ethereum blockchain is immutable. However, contents of state variables vary as account balances change. A solution is to save them off-the-chain.
• Oracle: We have just talked about that.
• Digitized assets: Commonly digitized assets require a large dataset to describe/define them. Given a limited size of blocks, it is not feasible for hosting complete asset information on a chain.
• Trimmed blocks: For optimization, Ethereum full nodes need to keep a portion of the distributed ledger, that is, to trim a ledger. The trimmed blocks are saved off-the-chain at a centralized location for supporting future inquiries.