Disadvantages of data redundancy include an unnecessary increase in size of databases, and the likelihood of data corruption being a direct result of redundancy. Other disadvantages include the likelihood of inconsistency of data as well as decreased efficiency of a database.
Data redundancy is a very common attribute of the modern computer database. Fundamentally, it is a repetition of data within a database. It can appear within a table as repeated data, or it can appear by itself. It is typically not something that the programmer intended to be part of the system, however, it is a by-product of programming without forethought.
Data redundancy can occur in databases that list clientele and customer information. If a customer gives information two separate times during two separate visits, now the customer's information is entered twice in the database and all fields are duplicated. If the system is smart enough to catch repeated information, then the customer's name will only exist one time in the system. A name could also appear several times if a customer visits separate locations of the same chain store. If the databases are not synced well with one another, duplication could occur. Too many instances of extra data such as this can lead to an overloaded hard drive due to the excessive backup of useless data.