What is the name of situation where the same data is stored unnecessarily at different places?

Data redundancy.

Explanation:

A database management system (DBMS) can be defined as a collection of software applications that typically enables computer users to create, store, modify, retrieve and manage data or informations in a database. Generally, it allows computer users to efficiently retrieve and manage their data with an appropriate level of security.

A data dictionary can be defined as a centralized collection of information on a specific data such as attributes, names, fields and definitions that are being used in a computer database system.

In a data dictionary, data elements are combined into records, which are meaningful combinations of data elements that are included in data flows or retained in data stores.

Data redundancy is the name of situation where the same data is stored unnecessarily at different places.

Simply stated, data redundancy can be defined as a condition which typically involves storing the same data in multiple storage locations. Thus, data redundancy connotes the unnecessary repetition of the same piece of data (informations) either deliberately or for some specific reasons.