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1、Module8DiskArchitectureDiskArchitecture11-20038-1?2001,2003InternationalBusinessMachinesCorporationObjectivesAttheendofthismodule,youwillbeableto:?DescribetheDynamicServerchunkandpagestructure?Explainhowpagesareallocatedwithinextents?Explainthedifferencebetweentableandindexextents?Descri
2、betherelationshipbetweenchunksandDBSPACES?Describetheoverheadpagesinvarioustypesofchunks?Describethestructureofadbspace,blobspace,andsbspace?Usetheoncheckcommandtodisplayreportsaboutspaceallocation,tblspaceusage,andindexusage?Useonstattodisplaydbspaceandchunkinformation8-28-2DiskArchitec
3、tureUnitofPhysicalDiskSpace:Chunk/dev/rxy0h/dev/chunk110000KB10000KBUnix(cooked)fileRawDevicePieceofRawDevicepath=/dev/cook-001path=/dev/raw-001path=/dev/raw-001offset=0KBoffset=0KBoffset=5000KBsize=10000KBsize=10000KBsize=10000KB/dev/rxy0f5000KB20000KB10000KB8-3Achunkisaunitofdiskorphys
4、icalspacethatisassignedtotheserver.Achunkcanbearawdevice(character-specialdevice),apieceofarawdevice,oraUNIXfile(cookedfile).Whenyouassignachunktotheserver,youdefinethechunkusingthefollowingthreevalues:PathnameThepathnameofthefileortherawdevicenametobeusedforthechunk.OffsetThephysicaldis
5、tance,specifiedinkilobytes,fromthebeginningofthedevicetowherereadingandwritingforthedevicebegins.Ifcreatingchunksthatusecookedfiles,useanoffsetof0.Anon-0offsetisonlytobeusedforrawdevices.SizeTheamountofspace,specifiedinkilobytes,allocatedtobeusedinarawdevicestartingfromtheoffset,orthesiz
6、eoftheUNIXfileusedforthechunk.ChunkLimitAserverhasalogicallimitof32,767chunks(thelimitis2047chunksinpre-9.4versionsofIDS).However,theUNIXkernelmighthavealimittothenumberoffilesaprocesscanhaveopenthatsupersedestheserverlimit.DiskArchitecture8-3EnablingLargeChunkSupport(9.4)Enablelargechun
7、ksupportbyexecutingthefollowingcommand:onmode-BCnwherenisoneofthefollowingconversionstagelevels:?Stage1?Largechunksandlargeoffsetsenabled?Writestosmallchunkscontinuetouseoldpageformat?Reversionisstillpossible?Stage2?Allpagesareconvertedto9.4formatastheyaremodifiedduringno
