i) CRUD functions

  • Must enable users to create data structures.

  • Retrieve data from data structures.

  • Update these data structures.

  • And delete data structures

ii) Data dictionary

  • Must support a repository of meta-data.

  • Holds data about structure, relationships and integrity constraints.

  • Holds data about names and authorization privileges associated with users.

iii) Concurrency control

  • Must enable many users to access same data at the same time.

  • And ensure that the database is not left in an inconsistent state when this occurs.

iv) Recovery

  • Must ensure that the database can recover from software or hardware failure that damages it in some way.

Describe a data dictionary. Indicate when the data dictionary is used and by whom.

  • A data dictionary is a means for recording the meta-data of some organisation.

  • Also known as system catalog.

  • Typically stores data about the structure of data, relationships between data items, integrity constraints expressed on data, the names and authorization privileges associated with users.

  • The DD effectively implements the three-level architecture of a DBMS.

  • It is a method of recording the data resources and data requirements which can be used during analysis and design as well during implementation.

  • It is the main tool used by the data administrator and database administrator.