# Data catchups/backfill Mercury's Data Catchups feature allows you to backfill historical data for your programs. It generates artificial ledger transitions for past events, enabling you to retrieve and process data from before your program creation. This feature is ideal for projects requiring complete historical records or starting indexing mid-way through a contract's lifecycle. Data Catchups seamlessly integrate past data with your current indexing, ensuring a comprehensive view of on-chain activities without modifying your existing logic. Learn more in the dedicated section: [Data Catchups/Backfill](/zephyr-full-customization/learn/data-catchups-backfill.md). --- # 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://docs.mercurydata.app/zephyr-full-customization/learn/get-started-set-up-and-manage-the-project/data-catchups-backfill.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.