第五章 分布式数据库概述
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, , , , OO, , , , , , , , , , , , Cluster, Web, , , ,
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--, ,- DBA, ,
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:PM..., ...
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: . Site, , Site. Site, , . Site(LDB)DBMS, .
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: London, New York .:EMP(ENO, NAME, TITLE, SALARY, ):
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, E.g. , ,
, E.g. E.g. ,
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EMPLondonPayroll appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei Jing !
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LondonEmpLondonPayroll appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingBJEmpNYEmp!!
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LondonPayroll appAnnual Bonus appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingLondonEmpNYEmpBJEmp
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LondonPayroll appAnnual Bonus appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingLondonEmpNYEmpBJEmp,
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LondonPayroll appAnnual Bonus appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingLon, NYEmpNY, BJEmpBJ, LonEmp
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RDBMSFilestape
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(Homogeneous)SiteDB, (Heterogeneous)SiteDB. DDBSieSiteCopyDDB, SiteCopy(Site), Copy(Site)
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, , :
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(1) PPP...M
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-(2) ......MM
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-(3) ...
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DDB LDDLDBGDDGDB
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LDBMSDBCMDDDDBMS
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111nnn..DDBMS
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DBMSDBMSDBMS1234
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DB!DBDB (, )
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DB:(Fragmentation): (Allocation):
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: I/O:!
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:LockingTimestamps
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::
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:Rain>1700mm,,. wine(year, name, producer, area, country) weather(year, area, country, sun, rain) winecountry, , . Weatherweather-R(year, area, country, rain) weather-S(year, area, country, sun).
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-weather-R, , , , . = 3*18000+400+800+200 = 55400bytes wine-F, wine-I, wine-U , , . = 12000+15000+20000+1400 = 48400bytes
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()DDBDB
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, .: Supplier Supplier1 Supplier2 : Supplier1 Site1 Supplier2 Site2Site3(1) Read (Terminal, $S#)SELECT sname INTO $snameFROM SupplierWHERE s#=$S#;Write(Terminal, $sname);
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(2) Read(Terminal, $S#);SELECT sname INTO $snameFROM Supplier1 WHERE s#=$S#;if not found THEN SELECT sname INTO $sname FROM Supplier2 WHERE s#=$S#;Write (Terminal, $sname);
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(3) Read(Terminal, $S#);SELECT sname INTO $snameFROM Supplier1 AT Site1WHERE s#=$S#;if not found THEN SELECT sname INTO $sname FROM Supplier2 AT Site2WHERE s#=$S#;Write (Terminal, $sname);
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(4) Read(Terminal, $S#);EXECUTE $SUPIMS($S#, $FOUND, $sname) AT Site1;IF not found THEN EXECUTE: $SUPCODASYL($S#, $FOUND, $sname) AT Site2;Write(Terminal, $sname);
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2003
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Ceri 1984 1992< > 1998 1999M. Tamer Ozsu and Patrick Valduriez, "Principles of Distributed Database Systems," Second Edition, Prentice Hall 1999.
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