Design And Implementation Of Data Dictionary In Da Meng DBMS

A data dictionary is an important part of a database, which holds information about the meta-data of the database. Data dictionaries do not contain any actual data from the database, only bookkeeping information for managing it. Any well-designed database will surely include a data dictionary, it provides database administrators and other users, easy access to the type of data that they should expect to see in every table, row and column of the database, without actually accessing the database.Without a data dictionary, however, a database management system cannot access data from the database. a data dictionary becomes a crucial necessity.DBMS constantly accesses the data dictionary during database operation to validate user access and to verify the state of schema objects. DBMS also updates the data dictionary continuously to reflect changes in database structures, auditing, grants, and data.Consequently, all data dictionary information is stored in CACHE. In this paper, we desigin a secondary cache model to access the data dictionary with high performance.Since a database is meant to be built and used by multiple users, making sure that everyone is aware of what types of data each field will accept becomes a challenge, especially when there is a lack of consistency when assigning data types to fields. A data dictionary is a simple yet effective add-on to ensure data consistency.Concurrency is the central of data dictionary cache.This paper throughly disscuss a lock based concurrency control model, getting to good result in concurrency.