A record refers to a single row or entry in a database table that contains information about a specific entity or object.
Fixed Length Records
We can store fixed length records in two ways:
- packed: no gaps between records, record ID is location in page
- unpacked: allow gaps between records. The unpacked page use a bitmap to keep track of where the gaps are.
Variable Length Records: Slotted Pages
Move header to end of a page to allow it to grow. It also stores number of slots and pointer to free space.
As the pic shows (left), deletion with unpacked layout could cause fragmentation.