, , , , OO, , , , , , , , , , , , Cluster, Web, , , ,

--, ,- DBA, ,

:PM..., ...

: . Site, , Site. Site, , . Site(LDB)DBMS, .

: London, New York .:EMP(ENO, NAME, TITLE, SALARY, ):

, E.g. , ,

, E.g. E.g. ,

EMPLondonPayroll appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei Jing !

LondonEmpLondonPayroll appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingBJEmpNYEmp!!

LondonPayroll appAnnual Bonus appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingLondonEmpNYEmpBJEmp

LondonPayroll appAnnual Bonus appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingLondonEmpNYEmpBJEmp,

LondonPayroll appAnnual Bonus appLondonNew YorkPayroll appNew YorkBei JingPayroll appBei JingLon, NYEmpNY, BJEmpBJ, LonEmp

RDBMSFilestape

(Homogeneous)SiteDB, (Heterogeneous)SiteDB. DDBSieSiteCopyDDB, SiteCopy(Site), Copy(Site)

, , :

(1) PPP...M

-(2) ......MM

-(3) ...

DDB LDDLDBGDDGDB

LDBMSDBCMDDDDBMS

111nnn..DDBMS

DBMSDBMSDBMS1234

DB!DBDB (, )

DB:(Fragmentation): (Allocation):

: I/O:!

:LockingTimestamps

::

: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).

-weather-R, , , , . = 3*18000+400+800+200 = 55400bytes wine-F, wine-I, wine-U , , . = 12000+15000+20000+1400 = 48400bytes

()DDBDB

, .: Supplier Supplier1 Supplier2 : Supplier1 Site1 Supplier2 Site2Site3(1) Read (Terminal, $S#)SELECT sname INTO $snameFROM SupplierWHERE s#=$S#;Write(Terminal, $sname);

(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);

(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);

(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);

2003

Ceri 1984 1992< > 1998 1999M. Tamer Ozsu and Patrick Valduriez, "Principles of Distributed Database Systems," Second Edition, Prentice Hall 1999.