# Immutable Transactions and Pruning Once transactions are confirmed and included in a block, they become **immutable**, meaning they cannot be altered or deleted. This immutability allows nodes to prune their records by removing references to spent transactions, thereby optimizing storage. The process of **pruning** involves retaining **only the necessary data to validate the remaining transactions**. As nodes discard older transactions, they **maintain the parent hashes** to ensure that the integrity of the blockchain is preserved. This **selective retention of dat**a allows nodes to operate efficiently without the burden of storing every transaction indefinitely. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://hub.bsvblockchain.org/higher-learning/bsv-academy/bitcoin-whitepaper-series/section-7-reclaiming-disk-space-bitcoin-whitepaper/immutable-transactions-and-pruning.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.