Storage Manager
- The database is stored as a collection of files.
- A file is implemented as a collection of pages. In most database systems, each file corresponds to a single table or index.
- Each page contains, depending on its type:
- Table page: a header, metadata, and multiple table records.
- Index page: multiple index entries.
- A table record is a sequence of fields.
Database Pages
- A page is a fixed-size block of data.
- Ranges from 1KB to 64KB, typically 4KB
- It can contain tuples, meta-data, indexes…
- Most systems do not mix page types.
- Each file has records of one particular type only
- Some systems require a page to be self-contained
Record Layout
- A record is essentially a sequence of bytes.
- It's the job of the DBMS to interpret those bytes into attribute types and values.
- Schema information is stored in DB catalog, store the sizes of fixed-length fields
- Records are stored as a collection of pages