Data Layout on Disk
Explore how databases structure data on disk with fixed-size pages and how slotted pages address fragmentation from variable record sizes. Understand the role of pointers, metadata headers, and allocation algorithms in efficient page management, plus the use of overflow pages for large records. This lesson provides insight into organizing data for optimized storage and retrieval.
We'll cover the following...
Database systems store the data on filesystems in the disk. The system further breaks down files into fixed-size units called pages. A page is a basic structure to organize data and index files on disk and the data transfer unit. Each page in the filesystem can hold from 4kb to 16kb.
Fixed-size page
The layout with fixed-size pages includes a group of pages, each with a constant size. A page or group of pages includes records of primitive and complex types. Every page contains data and a pointer to the next page. Each record on a fixed-size page should fit into a page. If the record size exceeds the page size, the layout uses pointers to connect multiple pages to store a single record.
The major problem with fixed-size pages is variable-size records. If the record size is less than the size of the page, the layout can only partially fit the data record. Unfortunately, this process leads to ...