Database Research Essay

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2. What is metadata? Which component of a DBMS maintains metadata? Metadata is data in a database and includes descriptions about tables and definitions of fields. Metadata is contained in the DBMS's catalog. 4. What is meant by concurrent update? Concurrent updates occur when several users are trying to access and edit the same information at one time. 6. What is locking, and what does it accomplish? Locking is where once one user accesses the information within a part of the database all other users are blocked from accessing it until the first user is finished working in that area. This takes care of concurrent updates by not allowing more than one user to access information at a time. 8. Describe two-phase locking. It a possible way that a database takes care of concurrent updates. It comes in two parts: the growing phase - DBMS locks rows and doesn't release anything and shrinking phase - the DBMS releases all its locks and doesn't lock anything else. 10. How do some DBMSs use time stamping to handle concurrent update? Using time stamping, a database is able to handle concurrent updates. If more than one users is trying to make changes at the same time, then once the first user is finished making his changes it stamps the changes with the time they were completed and when the second user is finished it stamps those changes with another unique time. So it allows for multiple users to access and edit the data simultaneously, and the database stores these changes until it is time for the update. Each day or at another time specified by the DBMS, the database begins updating. It starts with the first timestamp and works it's way through the list so that the updates occur in the order in which they happened so the new information is correct. 12. What is journaling? What two types of images does a DBMS output to its journal? Journaling

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