Variable length fields are used or highly variable data such as descriptive data. Database data is normally access either by sequential or random access methods. Sequential access is accomplished when data is arranged in contiguous, linear fashion. An example of this method is tape storage. Sequential access is easy to program, however, it is generally slower than the random access method.
Random access allows access to any data located on the storage device in a non-linear fashion.
Database Management System. A DBMS has several consistent parts. The database definition language is the part of the DBMS that allows the user to set up the database, to specify how many attributes there will be and how they are defined and manipulated. The data dictionary contains a catalog of all the attributes with their legal values and ranges. Use of a query language allows a user to perform advanced functions such as sorting, reordering, subsetting, and searching.