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10 Cards in this Set
- Front
- Back
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Drawbacks for using a File System
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-Even if we do, on 32-bit computer systems we cant directly refer to more than 4gb of data. So we have to program an identifying method for all data items.
-Have to write special programs to answer each question users ask about data (likely to be complex because of large volume of data to be searched-Must protect data from inconsistent changes made by different users accessing the data at the same time (concurrently). If apps have to address the details of such concurrent access, this adds more to the complexity. -Must ensure data is restored at a consistent state if the system crashes while changes are being made.-OS provides only password mechanism for security. - Not sufficiently flexible to enforce security policies in which different users have permission to access different subsets of data. |
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DBMS purpose
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To alleviate drawbacks of using File System - manage data in a robust and efficient matter for a large # of users/data.
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Advantages of a DBMS
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-Data Independence -Efficient Data Access -Data Integrity and Security -Data Administration -Concurrent Access and Crash Recovery -Reduced Application and Development Time
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Data Independence
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Application programs should not be exposed to details of data representation and storage - DBMS gives an abstract view of the data that hides the details.
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Efficient Data Access
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A DBMS utilizes a bunch of complex techniques to store/retrieve data efficiently. (** vital for data put on external storage devices)
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Data Integrity and Security
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If data is always accessed through DBMS – DBMS can apply integrity constraints (IE. Can’t insert data about employee pay if > budget of company). DBMS can also enforce access controls to govern what data is visible to whom.
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Data Administration
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When several users share the data, centralizing the administration of data can offer improvements. - Let the more experienced data guy handle it to make data retrieval more efficient and minimize redundancy.
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Concurrent Access and Crash Recovery
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DBMS schedules concurrent accesses to the data in such a manner that users can think of the data as being accessed by only one person at the same time. - DBMS also protects users from system failure effects.
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Reduced Application Development Time
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DBMS supports important functions that are common to many applications accessing data in the DBMS + high-level interface to the data makes for quick application development. DBMS apps are likely to be more robust than similar stand-alone apps because many important tasks are handled by DBMS (no need for debug/test in the app).
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Disadvantages of using DBMS
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-complex software -optimized for certain kinds of workloads (ie. answering complex queries or handling many concurrent requests)-its performance might not be adequate for certain specialized applications. (ie. apps with real-time constraints or a few well-defined critical operations for which custom code has to be written).
-An application may need to manipulate data in ways not supported by Query Language. -If specialized performance/data manipulation requirements are central to an application – DBMS might not be a good choice – especially if benefits of DBMS are not required. (flexible querying, security, concurrent access and crash recovery) |
