Consider a relation stored as a randomly ordered

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1.Answer the following questions about data on external storage in a DBMS: 

1. Why does a DBMS store data on external storage? 

2. Why are I/O costs important in a DBMS? 

3. What is a record id? Given a records id, how many I/Os are needed to fetch it into main memory? 

4. What is the role of the bu?er manager in a DBMS? What is the role of the disk space manager? How do these layers interact with the ?le and access methods layer?

2.Consider a relation stored as a randomly ordered ?le for which the only index is an unclustered index on a ?eld called sal. If you want to retrieve all records with sal > 20, is using the index always the best alternative? Explain.

Reference no: EM13509476

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