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