# Database Pages A page is a fixed-sized block of data * It can contain tuple, metadata, indexes, log records... * Most systems do not mix page types * Some system require a page to be self-contained Each page is giving a unique identifier * The DBMS uses an indirection layer to map page ids to physical locations There are 3 different notions of "pages" in the DBMS: * Hardware page (usually 4KB) * OS Page (usually 4KB) * Database Page (512B - 16KB) By hardware page, we mean at what level device can guarantee a "failsafe write" ![](/files/rm0lEVbwwh8nFhOnnJSc) --- # 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://til.notdu.com/database/intro-to-database-systems/database-storage/database-pages.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.