A data dictionary is a database containing information about the structure of another database. Data dictionaries hold the names and characteristics of data in a database and outline relationships between data.
Data dictionaries are not meant for most users, as an inexperienced hand could do a lot of damage to the primary database if allowed to work freely in a data dictionary. For this reason, data dictionaries can typically only be accessed by a select few—most often those who work to maintain and control the database.
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