Chapter6

Chapter6 - CSIS0278A CSIS0278A IntroductiontoDatabase...

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CSIS0278A CSIS0278A Introduction to Database  Introduction to Database  Management Systems Management Systems Lecture 6  Storage and File Structure Dr. Reynold Cheng Based on the Ch. 11 notes of “Database System Concepts” by A.  Silberschatz, H. Korth & S. Sudarshan and notes by Dr. Ho Wai  Shing
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DB070:2 Motivation Motivation Our  database Where to store these data? access speed reliability cost capacity Study the factors, study the technology, choose the best  solution. Understand the  situation, and choose different technology under different situation. (e.g., main copy? query evaluation? backup? )
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DB070:3 Motivation Motivation Where do we store the databases?   Target: as cheap as possible, and as fast as possible  under all situations. Study the technology, to understand where the  balance point is. Speed  – Different storage media may have different  access time over different situation / access  patterns. Capacity  – Can the storage media store all required  data? Cost  – Usually, faster media has a higher per-unit  cost
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DB070:4 Motivation Motivation How do the physical characteristics of storage  devices affect the DBMS’s performance, and the  design of databases? e.g., for the same amount of data, over which parts of the  hard-disk should we place our data? How data are transferred and managed between  disks and main memory? How does the DBMS store a relation on disk?  How  are records (tuples) organized in such a file?  How  is the performance affected by this? Goal: To improve the performance by making  educated choices.
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DB070:5 Overview Overview Storage Hierarchy Magnetic Disks Buffer Management File Organization
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DB070:6 Overview of DBMS & Storage  Overview of DBMS & Storage  Systems  Systems  Applications DBMS (Relations) in memory File System (files) in Buffer (memory) + disk Storage System on  disk (blocks)                                      SELECT name FROM Student WHERE …  name John Peter Mary Return records from the student file (say, student.myd ). Parts of file (in memory or disk) storing the data
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DB070:7 Physical Storage Media Physical Storage Media Three important factors: Speed   (how fast can the data be accessed?) Cost    (how much is it to store one unit of data?) Reliability Do we have data loss on power failure or system crash? Do we have data loss due to physical failure of device?
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This note was uploaded on 12/01/2010 for the course CS 0278 taught by Professor Dr during the Spring '10 term at HKU.

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Chapter6 - CSIS0278A CSIS0278A IntroductiontoDatabase...

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