Similarly, changing and deleting records also requires that all records be rewritten. Searching the database is done by linear search or index search. Searching a flatfile database normally requires that the entire text of the database be searched. Faster searches can be done if the database is indexed. For example, the Cell Stock database above could be indexed by Experiment, Plasmid, Species, etc.
Indexing can greatly increase the size of the database.
Flatfile databases force a single view of the data Probably the single most important disadvantage of flatfile databases is that the records must be organized by one of the fields. In the example, the decision would have to be made that the Cell Stock was the fundamental unit of data, and that other types of information, such as Plasmids or Species, were best considered as an attribute of a Cell Stock. For many purposes, this is an unnatural representation of the data. GenBank entries retrieved by Entrez are flatfile representations of data that are centered around DNA sequences. In a GenBank entry, every field appears to belong to a particular sequence.