Concise Guide to Databases: A Practical Introduction (Undergraduate Topics in Computer Science)
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This easy-to-read textbook/reference presents a comprehensive introduction to databases, opening with a concise history of databases and of data as an organisational asset. As relational database management systems are no longer the only database solution, the book takes a wider view of database technology, encompassing big data, NoSQL, object and object-relational and in-memory databases. The text also examines the issues of scalability, availability, performance and security encountered when building and running a database in the real world. Topics and features: presents review and discussion questions at the end of each chapter, in addition to skill-building, hands-on exercises; introduces the fundamental concepts and technologies in database systems, placing these in an historic context; describes the challenges faced by database professionals; reviews the use of a variety of database types in business environments; discusses areas for further research within this fast-moving domain.
can be used to purchase goods and services you also ‘give’ the card owner a lot of information about your buying habits. What you bought, where you bought it, when you bought it and how you bought it are all captured at the point of sale. Because you will have given them other information such as your age, address and gender, this can also be cross-referenced and other information generated, for example, how far from home your purchase was made and was it likely to have been made on your way to
(original at http://www.computer-history.info/Page4.dir/pages/Univac.dir/, last accessed 07/08/2013) 2.3 Sequential Systems Initial computer systems processing data were based on the pre-existing manual systems. These were sequential systems, where individual files were composed of records organised in some predetermined order. Although not a database because there was no one integrated data source, electronic file processing was the first step towards an electronic data based
to do with the handling of the data. Again, the examples here are Oracle specific, but the principles will be present in other RDBMS. Information The term Instance is used to describe the processes and structure that exist in an Oracle server. In Oracle terminology, the Server is the Instance plus the disks based information, which it calls the database. As its name suggests, the System Monitor’s major task is to make sure the instance is running OK. If need be it can perform a recovery when
The change vector is written BEFORE the commit is actioned. This means that if the user gets confirmation that their commit has been processed, the data post-commit can be replaced even if it was not written to disk before the instance failed. Redo logs are clearly an important part of ensuring robustness. Again, Oracle allows these files to be multiplexed, that is two or more identical copies of log are automatically updated in separate locations to guard against a disk failure on the disk
becoming a popular offering by providers. As this allows an organisation to have redundant data spread across the world the service offers potentially more security than having servers in one geographical location. 10.2.1.5 Using RAID to Improve Availability Some organisations will not be looking to the Cloud for some time to come. Those that worry about security, or which have recently invested heavily in internal infrastructure, will still want to ensure their databases are as available as