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1、informix逻辑日志和物理日志Thephysicallogandlogicallogsintheinformixdatabasearetwoveryimportantdiskartifacts・1.ThephysicallogPhysicallogisacontiguousdiskspace・Themainpurposeistoprovidetherawdataimagefortherapidrecoveryofthesystem・Physicalloginpagetoallocateandreleasefortheunit,itiscalledb
2、eforethecontentofstoredimages(asthenamesuggests,theappearanceoftheoriginaldatabeforemodifyingthedataimage)・WhenoneofSharedmemorypagestobemodifiedbefore(modified)forthefirsttime,systemtomodifythedatabeforefirstimage()beforeimagesstoredinthephysicallog.Thus,beforetheentireoperatio
3、noftheuserisfullysuccessful,themodifiedimageofallthedatapageshehasmodifiedissaved,andoncetheproblemoccurs,Thesystemcanquicklyrecoverfrombeforeimagesinthephysicallog・Itisimportanttonotethatbeforethefirsttimethedatapagehasbeenmodifiedbeforetheimageissaved,Allchangestothepagearenol
4、ongerwrittenbeforeimageafterthebeforeimageiswrittenanditisreleased.Whentheuserwritesthispageandthelogicallogisreleased,Thebeforeimagecanbereleased.2.ThelogicallogsLogicallogsarecomposedofseveralseparatediskSpaces,eachacontinuousdiskspace・Thereareatleastthreelogicallogblocksforan
5、InformixDynamicServersystem,Themaximumdatacanbeconfiguredbytheadministrator(nomorethan32,767blocks)・Isthepurposeofthelogicallogwillremembertomodifysystemeachoperation,eacharesaved,sothatwhenthesystemproblemscanREDO(REDO)accordingtoitscontentortransactioncannotproceedtorollback(U
6、NDO)・Thecontentofthelogicallogrecordsmainlyconsistsoftheimpactofthetransactiononthesystem,theDDLstatement,andthecheckpoint(checkpoint)record・Physicallogsaremaintainedbythesystem,oftenwithoutmaintenance・Maintenanceoflogicallogs・BackupoflogicallogsFirst,thebackuplevelisalsounderst
7、oodbytheconceptofinformixThebackuplevelis0,1,20:afullbackup1:thelastfullbackup,incremental2:incrementsfromthelastincrementTherearetwotypesofbackup:automaticandcontinuousTheso-calledautomaticisnotimagined,itwillbeoverafterrunonce,sotheremustbeascriptorartificialtimingtobackupthel
8、ogicallogs,oritwillbefilled・Command:ontape-atos
