ca idms buffer tuning

World®’16

CAIDMS™BufferTuning

JohnSiraco,Director,SoftwareEngineeringCATechnologies

MFX106S

MAINFRAMEANDWORKLOADAUTOMATION

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Abstract

Thissessiongivesyouanoverviewofdatabaseandjournalbuffersandhowtheywork,aswellashowtotuneyourbuffersforperformance.YouwilllearnhowtosizeyourdatabaseandjournalbufferpoolsforperformanceandhowtotunebufferstoimprovezIIPusage.

JohnSiraco

CATechnologiesDirector,SoftwareEngineering

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Agenda

DEFININGANDCHANGINGADATABASEBUFFER

DEFININGAJOURNALBUFFER

ZIIPPROCESSING

THEDIFFERENCEBETWEENDATABASEANDJOURNALBUFFERS

HOWBUFFERSWORK

RECOVERY

1

2

3

4

5

6

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DefiningaDatabaseBuffer

§ Bullet1,Calibriregular24pt– Sub-bullet,Calibriregular20pt

§ Sub-sub-ullet,Calibriregular18pt– Sub-sub-subBullet,Calibri

regular16pt

§ Sub-sub-sub-subBullet,Calibriregular16pt

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DCMTDisplayBufferDEFAULT_BUFFER

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DCMTDisplayBufferDEFAULT_BUFFERLOC

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DCMTVaryBufferDEFAULT_BUFFERMAX100000

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DCMTVaryBufferDEFAULT_BUFFERINI20000

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DCMTVaryBufferDEFAULT_BUFFERADD10000

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DCMTVaryBufferDEFAULT_BUFFERCLOSE

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DCMTVaryBufferDEFAULT_BUFFEROPEN

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DCMTDisplayBufferDEFAULT_BUFFERLOC

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DCMTVaryBufferDEFAULT_BUFFER40000

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DCMTDisplayBufferDEFAULT_BUFFERLOC

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DCMTVaryBufferDEFAULT_BUFFER45000

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DCMTDisplayBufferDEFAULT_BUFFERLOC

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DCMTVaryBufferDEFAULT_BUFFER41000

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DCMTDisplayBufferDEFAULT_BUFFERLOC

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DCMTVaryBufferDEFAULT_BUFFER46000

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DefiningaJournalBuffer

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DCMTDisplayBUFFERJNL_BUFFER

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DCMTDisplayBUFFER

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DatabaseandJournalFilesandBuffers

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DatabaseandJournalFilesandBuffers

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DatabaseFilesandBuffers

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JournalFileandBuffers

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JournalFileandBuffers

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DatabaseReadIntobuffer

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DatabaseUpdateinBuffer

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AfterImageisBuiltinJournalBuffer

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WritetoJournal

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WritetoDatabase

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DatabaseUpdate,AllBuffersHave‘Mustwriteswitch’Set

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DatabaseUpdate,WriteJournalFirst

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JournalBufferandI/O

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JournalI/O

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JournalI/O

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JournalI/O

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DCMTDisplayBuffer

ThisshowsuponaDCMTDisplayBuffer,orDCMTDisplayBufferjournal-bufferas:WaitsonpriorI/O3:

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JournalI/OErroronRBN100

§ StopJournaling§ SetHighRBNto99§ Swaptothenextjournal§ CAIDMS™takesjournalbuffersforRBN100– 107andwritestothe

newjournal§ Restartjournaling

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JournalI/OErroronRBN100

§ Whenrecovery,eitherautomaticrecoveryorwarmstart,ortheArchiveJournalreadstheoldjournal,itwillstopatRBN99

§ TheywillnotreadRBN100§ EventhoughRBN102,103and105weresuccessfullywrittentotheold

journal,thehighRBNof99willstopCAIDMSfromaccessingRBNs102,103and105

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DCMTDisplayBuffer

ThisshowsuponaDCMTDisplayBuffer,orDCMTDisplayBufferjournal-bufferas:Waits0

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DCMTDisplayBuffer

§ Ifyouhave8journalbuffers,andallarewaitingforI/O,the9thtransactionwillwaitforajournalbuffer.

§ ThisshowsuponaDCMTDisplayBuffer,orDCMTDisplayBufferjournal-bufferas:Waits1

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JournalBufferandI/O

§ IftheWaitcountisanythingbut‘0’,thenaddbufferstothejournalbuffer§ Anadditional1or2makeatremendousdifference

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JournalI/O

§ IfWaitsonPriorI/Oishigh,thenthebottleneckismostlikelythejournalitself

§ TheI/Oistakingtoolong- addingbufferstotheJournalBufferwillNOThelpthesituation

§ Talktothesystem’sgroup,andseeiftheI/Ospeedtothejournalcanbeimproved

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JournalBufferPool- Recovery

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DCMTDisplayBuffer

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JournalBufferPoolRecovery§ Recoverywilllookinthejournal

buffersfirst,toseeifthejournalimagesarestillinthebuffers

§ Iftherearemorejournalimagesthatarenotinthebuffers,CAIDMSwillreadthejournalbackwards

§ MostDASDisCachedatthedevicelevel– Cacheworkslikeabufferpoolhowever,itisbuilttoworkinaforward

direction,notbackwardslikerecovery– Warmstart willreadthejournalbackwards– Makesureapplicationsissuecommits,sowarmstart doesnothavetoread

manyblocksbackwards

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zIIPProcessing

§ TheonlyprocessingdoneinTCBmodeis:– I/O,SVCexecution,andUserModecode

§ ADS,COBOL,DBProcedures,SYSTEMExits

§ Allotherprocessingisdoneonthespecialtyprocessor(zIIP)

§ ByreducingI/O,youwillincreasezIIP utilization

§ IncreaseDatabaseBufferswherepossible

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Summary

§ IncreaseDatabasebufferstoreduceI/O

§ IncreaseJournalbufferstohelprecovery

§ ReducingI/OwillhelpzIIPprocessing

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