Alternatives for Data Entries (Contd.)
Alternatives 2 and 3:
- Data entries typically much smaller than data records. So, better than Alternative 1 with large data records, especially if search keys are small. (Portion of index structure used to direct search is much smaller than with Alternative 1.)
- If more than one index is required on a given file, at most one index can use Alternative 1; rest must use Alternatives 2 or 3.
- Alternative 3 more compact than Alternative 2, but leads to variable sized data entries even if search keys are of fixed length.