CA IDMS Deadlock Analysis

World®’16

CAIDMS™DeadlockAnalysis

JohnSiraco,Director,SoftwareEngineeringCATechnologies

MFX71E

MAINFRAMEANDWORKLOADAUTOMATION

2 ©2016CA.ALLRIGHTSRESERVED.@CAWORLD#CAWORLD

Abstract

Thissessionprovidesanexplanationofthelockingprocessandthepotentialdeadlocksituationsthatmayhappen.Thematerialpresentsthemessagesgeneratedwhenadeadlockoccursandtheiruseinidentifyingtheunderlyingcauseofthedeadlockscenario.Finallysomegeneralapplicationdesignrecommendationsarediscussedtominimizetheoccurrencesofdeadlocks.ThelastthreesectionsrelatetoCPUsavingsoptions(zIIP),Multitasking,andtheuseofParallelSysplex options.

JohnSiraco

CATechnologiesDirector,SoftwareEngineering


Agenda

LOCKINGFUNDAMENTALS

DEADLOCKSCENARIOS

QUESTIONSANDANSWERS

LOCKINGERRORMESSAGES

DEADLOCKANALYSIS

GENERALRECOMMENDATIONS

1

2

3

4

5

6


LockingFundamentals

§ OurdatabasecontainsarecordtypenamedPRODUCTwhichcontainsafieldnamePROD-QUANTITY

§ PROD-QUANTITYrepresentsthequantityofthisproductthatisininventoryandavailabletobeshipped

Whydoweneedlocking?

PRODUCT

PROD-QUANTITY=2


LockingFundamentals

§ Tworun-unitssimultaneouslyaccessthisoccurrenceofthePRODUCTrecordwiththeintentofallocating2unitsoftheproductforshipmenttoacustomer.

§ Eachrun-unitseesthat2unitsareavailableandeachproceedtoupdatetherecordoccurrence

Whydoweneedlocking?

PRODUCT

PROD-QUANTITY=2

Rununit1

Rununit2OBTAIN OBTAIN


LockingFundamentals

§ Withoutlocking,eachrun-unitthinksithasallocated2unitsoftheproductforshipmenttoitsassociatedcustomerbutonlyatotalof2unitsexist

§ ThePROD-QUANTITYfieldissettozeroalthough2unitsmorethanavailablewereallocatedforshipment

Whydoweneedlocking?

PRODUCT

PROD-QUANTITY=0

Rununit1

Rununit2

MODIFY

MODIFY

Ships2units

Ships2units


LockingFundamentals

§ CAIDMSmaintainstwobasictypesofrecordlocks– SHAREDlocks

§ AlsoknownasRETRIEVALlocks§ Multiplerun-unitscanreadarecordoccurrenceandeachcanholdaSHAREDlockonthatoccurrence

§ Norun-unitmayacquireaSHAREDlockonarecordoccurrenceonwhichanotherrun-unithasanEXCLUSIVElock

TypesofRecordLocks


LockingFundamentals

§ EXCLUSIVElocks– AlsoknownasUPDATElocks– OnlyonerununitcanconcurrentlyholdanEXCLUSIVElockonarecord

occurrence– Norun-unitmayacquireanEXCLUSIVElockonarecordoccurrenceon

whichanotherrun-unithasaSHAREDlock

TypesofRecordLocks


LockingFundamentals

§ Lockingcontentionoccursinthefollowingscenario– Run-unit1readsthePRODUCTrecordcausingaSHAREDlocktobeset– Run-unit1thenmodifiesthePRODUCTrecordcausingitsSHAREDlock

tobeupgradedtoanEXCLUSIVElock

LockingContentions


LockingFundamentals

– Beforerun-unit1issuesaFINISHorCOMMITrun-unit2attemptstoreadthePRODUCTrecordoccurrencewhichtriestoestablishaSHAREDlockontheoccurrence.Thiscausesrun-unit2togointoawaituntilitcangettheSHAREDlock.

LockingContentions

PRODUCT

PROD-QUANTITY=0

Rununit1

Rununit2MODIFY OBTAIN

HoldsEXlock

WaitsonSHlock


LockingFundamentals

§ Whenrun-unit1issuesaFINISHorCOMMITitwillreleaseitsEXCLUSIVElockontherecordoccurrence

§ Run-unit2canthenacquiretheSHAREDlockanditsOBTAINcommandcanbecompleted

§ Run-unit2seesthecontentsoftherecordastheyweresetbyrun-unit1’sMODIFYcommand

LockingContentions


DeadlockScenarios

§ Basedonthesequenceinwhichrun-unitsaccessdatabaserecordsitispossiblethattwoormorerun-unitseachholdlocksonrecordoccurrencesrequiredbytheotherrun-unit

§ Whenthisoccursadeadlyembraceordeadlockoccursandoneoftherun-unitsmustbeabended


DeadlockScenarios(cont.)

§ Adeadlockoccursinourexamplewiththefollowingsequenceofevents– Run-unit1issuesanOBTAINagainstaPRODUCToccurrencecausinga

SHAREDlocktobeset– Run-unit2issuesanOBTAINagainstthesamePRODUCToccurrence

causinganotherSHAREDlocktobesetontherecord



– Run-unit1issuesaMODIFYagainsttherecordoccurrenceandgoesintoawaituntilrun-unit2releasesitsSHAREDlock

– Run-unit2issuesaMODIFYagainstthesameoccurrenceandgoesintoawaituntilrun-unit1releasesitsSHAREDlock

– Adeadlockconditionexistsbetweenrun-units1and2andmustberesolvedbyabendingoneoftherun-units


PRODUCT

PROD-QUANTITY=2

Rununit1

Rununit2OBTAIN

HoldsSHAREDlock

OBTAINHoldsSHARED

lock

MODIFYWaitsforEXCLUSIVE

lock

MODIFYWaitsforEXCLUSIVE

lock




§ Deadlockscanoccurbetweenmultiplerun-unitsandinvolvemultiplerecordtypes,recordoccurrences,orotherresources

RecordA RecordB

Rununit1

Rununit2

HoldslockHoldslock

Waitsforlock

Waitsforlock


LockingErrorMessages

§ Whenadeadlockconditionoccurs,aclusterofmessageswillbewrittentotheCV’slog

§ OneDC001000foreachtaskinvolvedinthelockingcontention


LockingErrorMessages(con’t)

§ OptionallyDC001001messagescanbegeneratedprovidingadditionalinformationaboutthelockingcontention– GeneratedwhenDEADLOCK_DETAILS=ONspecifiedintheCV’s

SYSIDMSfile– Twolinespertask

§ Onelinecontainingheaders§ Secondlinecontainingtheactualdata

§ ADC001002messageindicatingthetaskthatwasabortedaspartofthedeadlockresolution


LockingErrorMessages(cont.)

DC001000T:852690APPCP:APXPO031C:DEADWAITINGONR:LTXNLOCK0004200900397442

DC001001Txn/RUIDRUNAMESUBSCUserIDFE- ID1FE- ID2FE- ID3FETskcdDC001001451537594APXPO031APXSS100****

DC001000T:852711ADS2P:APXD1476C:DEADWAITINGONR:LTXNLOCK00052008008BDB94

DC001001Txn/RUIDRUNAMESUBSCUserIDFE- ID1FE- ID2FE- ID3FETskcdDC001001451537611APXD1476APXSS100C087415

DC001002T:852711ADS2P:APXD1476C:DEADDEADLOCKEDONR:LTXNLOCK00052008008BDB94

Onegrouppertask

Abending task



§ EachDC001000messagerepresentsataskthatisaparticipantinthedeadlockandiswaitingforaresource

§ Thefirst4fieldsofthemessageprovide:– Thetaskidofthewaitingtask– Thetaskcodethatinvokedthetask– Theprogramnamethatisbeingexecuted– Thestatusofthetask



§ Thelastfieldfollowingtheliteral‘R:’providestheresourceuponwhichthetaskiswaiting

R:<Type><wwwwxxyy zzzzzzzz>

Type- LTXNLOCK LocaltransactionlockGTXNLOCK GlobaltransactionlockPAGELOCK PAGELOCK

<wwwwxxyy zzzzzzzz>

<wwww> Pagegroup<xx> Codeidentifyingthevaluein<zzzzzzzz>

‘00’ <zzzzzzzz>containsadbkey (Recordlock)‘20’ <zzzzzzzz>containsapagenumber(SpaceManagementlock)‘80’ <zzzzzzzz>containsanarea’slowpage(Arealock)‘C0’ <zzzzzzzz>containsanarea’slowpage(Transientlock)‘01’ <zzzzzzzz>containsapagenumber(Pagelock)

<yy> Dbkey radix



§ ADC001001messageprovidesfurtherinformationtoassistinthedescriptionofthetaskdescribedintheprecedingDC001000message– Transactionid– ProgramnamefoundintheSUBSCHEMA-CONTROLwhentherun-unitwas

bound– Subschematowhichtherun-unitisbound



§ OneDC001001messagewillbedisplayedforeachrun-unitassociatedwiththewaitingtask

§ ADC001002messageisgeneratedtoidentifythetaskthatwasabortedtoresolvethedeadlock

§ ThecontentsofaDC001002isthesameastheassociatedDC001000butthespecifiedresourcecanbeinterpretedastheresourcethatwasthefinalitemcompletingthedeadlockscenario


DeadlockAnalysis

§ Itisextremelyrarethattheresolutionofdeadlockscanoccurbychanginganysystem-leveldefinitionswithinaCV

§ HoweverifaCVisexperiencingexcessivedeadlockstheCV’sSYSGENshouldbeexaminedforthefollowingstatements

DEADLOCKDETECTIONINTERVALIS1TICKERINTERVALIS1

§ Specifyingavalueof‘1’foreachoftheseoptionswillensurethatCAIDMSwillsearchforandresolvedeadlockconditionsassoonaspossible


DeadlockAnalysis(cont.)

§ Inanyenvironmentthatpermitsconcurrentupdatingofthedatabaseitistobeexpectedthatdeadlockswilloccur

§ Astransactionvolumeincreasessodoesthelikelihoodthatpointsofcontentionwilloccur

§ Deadlockconditionsarealmostalwaystheresultofthedatabasedesignandtimingissuesassociatedwiththewaytheapplicationnavigatesthedatabase

§ Resolutionwillusuallyrequiredatabasedesignand/orapplicationchangestoreducethepointofcontention



§ StartyourdeadlockanalysisbyscanningtheDC001000andDC001002messageslookingforrepeatingvalues

§ Ifasingledbkey ispresentinalargepercentageofthedeadlocksyouhaveprobablylocatedamajorpointofcontentionwithintheenvironment

§ TheDC001000/DC001002messagesdonottellyouthetypeofrecordrepresentedbythedbkey



§ UsethePRINTPAGEutilitytoprintthespecifiedpageandtoidentifythetypeofrecordinvolved

§ TheDC001000andDC001001messagescontaintheprogramandrun-unitnamesthatwereprocessingthedatabaseatthepointofthedeadlock



§ Thefollowinginnocentlookingcodecanresultinseriousdeadlockconditionswhichwouldbereflectedbyarepeatingdbkey intheassociateddeadlockmessages

OBTAINCALCORDER-CTRL.PERFORMIDMS-STATUS.MOVENEXT-ORD-NUMTOORDER-NUMBER.ADD+1TONEXT-ORD-NUM.MODIFYORDER-CTRL.PERFORMIDMS-STATUS.



§ TheORDER-CTRLrecordiswhatisknownasaOne-Of–A-Kind(OOAK)record

§ EverytimethatanorderisaddedtothedatabaseitisnecessarytoreadthesingleORDER-CTRLrecordtogetthenextordernumbertobeassignedandtomodifytherecord



§ Largenumbersoftransactionsconcurrentlyaddingorderscangenerateexcessivedeadlockoccurrences

§ Onepossibleresolutionwouldbetodevelopanalternatemethodtogenerateanordernumber

§ Anotheroptionwouldbetosingle-threadthiscodeusingENQUEUE/DEQUEUEcommands



§ Theproblemcodeinourexamplecouldbesingle-threadedasseenbelow

ENQUEUEWAITCTRL-LOCKLENGTH8.OBTAINCALCORDER-CTRL.

PERFORMIDMS-STATUS.MOVENEXT-ORD-NUMTOORDER-NUMBER.ADD+1TONEXT-ORD-NUM.MODIFYORDER-CTRL.PERFORMIDMS-STATUS.DEQUEUECTRL-LOCKLENGTH8.



§ Insomescenariostherepeatingresourcemaynotrepresentadbkey butapagenumber

§ Ifthevalueofthe<xx>portionoftheDC001000messageisx’20’thereisacontentionattemptingtomanipulatetheamountoffreespaceonthespecifieddatabasepage

§ UsethePAGEPRINTutilitytolistthespecifiedpage(s)todeterminethetypeofrecordsthatresideonthepage

§ UsethisinformationtoidentifytheassociatedlogicintheprogramsspecifiedontheDC001000andDC001001messages



§ Commoncausesofthistypeoflockcontentionarethefollowing– LargevolumesofrecordswrittentoasingleDCQueueusingaPUT

QUEUEcommand– LargenumbersofrecordsdefinedasDIRECTareaddedtoanarea

alwaysusing-1asthesuggesteddbkey– Manyrecordsalwaysaddedtothesamelocationwithinanindex

§ Single-threadingthesefunctionsorfindingalternativedatabasestructuresisrequiredtoresolvethesetypesofcontentions



§ Ifthevalueofthe<xx>componentoftheDC001000messageisanx’80’youhavecontentionontheusagemodeofadatabasearea

§ Usethepagegroupandpagenumbertoidentifytheareathatisinvolved

§ InspecttheprogramsspecifiedontheDC001000messagestodeterminehowtheyreadythearea



§ ThecommonprobleminthesecasesisprogramsthatattempttoreadyanareainaPROTECTEDorEXCLUSIVEmodeinanenvironmentwhereconcurrentprocessingisoccurring

§ ModifytheaffectedprogramstousedaSHAREDversionoftheREADYverb



§ InsomescenariostherepeatingvaluewithintheDC001000andDC001001maybeaprogramorrun-unitnames

§ Thisistypicallyanindicationthatthereisprogramlogicwithintheseprogramsthatcausescontentioninthesequenceinwhichvariousrecordsareaccessed

§ IdentifytherecordsandpagenumbersassociatedwiththeDC001000andDC001001messagesandusePRINTPAGEtoidentifythetypesofrecordsinvolved



§ IdentifythemostcommonsequenceofDMLcommandswithineachspecifiedprogramandlookforthosepointswherethevariousprogramlogicintersectsontherecordindicatedonthedeadlockmessages

§ Thesetypesofscenariosarebestaddressedbyapplicationstaffthatisfamiliarwiththelogicoftheprogramsinvolvedinthedeadlock



§ Resolutionofthesetypesofdeadlocksdependsontheoffendinglogicdiscoveredandtherequirementsoftheapplication

§ Thesetypesofdeadlockstendtobesporadicandusuallydonotgeneratelargenumbersofconcurrentdeadlockoccurrences



§ JREPORT008(JournalDetailReport)canbeausefulresourcetoassistindeterminingthesequenceofDMLcommandsinthesetypesofdeadlocks

§ LimityourJREPORT008executiontothosetransactionnumberslistedontheassociatedDC001001tominimizethegeneratedoutput

§ ThereportwillshowtheDMLcommandsandtheiraffecteddatabaserecordsinthesequencetheyoccur– Thiswillshowyouhowthedeadlockoccurred


GeneralRecommendations

§ Eachdeadlockscenariorepresentsauniquesetofconditionsbutthereareanumberofconsiderationsthatshouldbeobservedtominimizetheiroccurrence

§ Avoidrunningbatchupdatesduringonlinewindows– ExclusiverecordlocksarenotreleaseduntilIDMSisexplicitlytoldtodo

sothroughFINISHorCOMMITverbs– Batchupdaterun-unitsshouldincludefrequentCOMMITverbsto

periodicallyreleaselocks

§ Minimizetheamountofworkperformedbyasingleonlinetransaction


GeneralRecommendations(cont.)

§ Avoidcreatingdatabase‘hotspots’– Locateandeliminatesinglelocationswithinthedatabasethatmultiple

transactionsmustupdateconcurrently§ OOAKrecords§ DIRECTrecordsstoredusingasuggesteddbkeyof-1§ ADCqueue§ Indexstructurewherethesameorverysimilarkeyvalueisalwaysinserted



§ Avoidretainingresourcesacrosstransactionsorinteractionswithaterminaloperator– Longtermlockscanbeheldacrosstransactionsandcanlockadbkey

forlongperiodsoftime§ Theirusageshouldbeusedonlywhenabsolutelynecessary

– Don’tuseconversationaltasksthatkeepupdaterun-unitsopenwhilewaitingfortheterminaloperator’sresponse



§ Stresstestchangespriortoproductionimplementation– Anymodificationthatchangesthesequenceorvolumeofupdatesto

databaserecordsshouldbestresstestedatthelargestexpectedvolumeofconcurrenttransactions

– UseathirdpartyproductforyourstresstestsuchaTPNSfromIBM



§ Stresstestchangespriortoproductionimplementation– Anymodificationthatchangesthesequenceorvolumeofupdatesto

databaserecordsshouldbestresstestedatthelargestexpectedvolumeofconcurrenttransactions

– UseathirdpartyproductforyourstresstestsuchaTPNSfromIBM


SectionSummary

§ Deadlockanalysisismoreofanartthanasciencewhichrequirestheparticipationofasite’sapplicationstaffandnotjusttheDatabaseAdministrator

§ AlthoughtheDBAmaydotheinitialanalysisofthedeadlockmessagesgeneratedbyCAIDMSitwillusuallyrequiretheapplicationdeveloper’sspecializedknowledgeoftheapplicationcodetointerpret,identify,andcorrectanyunderlyingproblems


CPUSavingsOptionswithzIIP


SectionOverview

§ AmajorenhancementintroducedonRelease17wastheabilityofCAIDMS™toexploittheIBMzIIPspecialtyengineonthezSystem.EnhancementsmadeonthecurrentlysupportedreleasesofIDMS,versions18.5and19.0,havesignificantlyincreasedtheamountofCPUcyclesoffloadedtothezIIPspecialtyengines


SectionTopics

§ Termsanddefinitions§ Benefits§ Operationalconsiderations§ zIIPexploitation§ ImplementingviaCAIDMSstartupparameters§ Architecturechanges§ Eligibilityandrequirements§ EvaluatingbenefitwithoutaphysicalzIIPengine§ RealWorldexampleofbenefitoffloadingcycles


TermsandDefinitions

§ Enclave– Anenclaveisarepresentation

ofabusinesstransactionorunitofwork

§ TCO– Totalcostofownership

§ WhiteSpace– CPCPUcyclesmadeavailable

bymovingprocessingtoazIIPprocessor

§ zIIP– IBMSystemzIntegrated

InformationProcessor§ CPorGP

– GeneralPurposeProcessor§ TCB

– OperatingSystemTaskControlBlock

§ SRB– OperatingSystemService

ControlBlock


Benefits

§ Cost/benefittradeoff– SiteswithzIIPcapacity– SitesnearingCPcapacity

§ CosttoaddazIIPversuscosttoaddaCP– Hardware(zIIPisless)

– Softwarelicensingfees(zIIPisnone)

§ BenefitofzIIPversusCP– DependsonhowmuchworkloadcanbeoffloadedtozIIP


Benefits

§ TestinghasshownbenefitsforallCAIDMSworkloadsandenvironments– CICS,CAADS™,DCCOBOL,CAIDMS™Server,etc– Aswellasvaryingmixturesoftheaboveworkloadsandenvironment– Bestconfiguration,mostCPUcyclesoffloaded,willbewhenanIDMS

systemisusedasabackend§ CICStransactions,ServerorDistributedtransactions,BatchtoCVwork(CVsideonly)


zIIPExploitation

§ WhyzIIPs?– Lessexpensivethangeneralpurpose

processors– NosoftwarechargesforzIIP capacity– OffloadingcyclestozIIP freescycleson

CPforadditionalwork§ Deferprocessorupgrades§ Increasethroughput

GeneralPurpose Processor

near 100% busy

GeneralPurpose

Processor

zIIP

IncreaseWhiteSpaceonCPs


CAIDMSzIIPExploitation

§ 100%CAIDMSsystemsupportcodeiszIIP eligible– ExecutesinSRBmode zIIPCP

CA IDMS Workload

TCBmode

SRB mode


ImplementingviaCAIDMSStartupParameters

§ Controlledbystartupparameter– Startupparameters

§ zIIP=Y– UsethezIIP feature

§ zIIP=N– DonotusethezIIP feature

– DefaultifzIIP parameterisomitted

§ ImpactonExistingDialogsandPrograms:None!– Allexistingdialogs,programs

ofanylanguage,willruninanenvironmentcontainingzIIPprocessorswithoutchangeorimpact§ OtherthananoverallreductioninCPCPUusage


EligibilityandRequirements

§ Loadingofnucleusmodule,linedrivers,servicedrivers,RHDCUXIT,DBproceduresmustbefromauthorizedlibraries

§ Additionalauthorizedlibraries

§ DetailedmessagesforerrorsIDMSDC016106ZIIP=Nforced.Moduleaaaaaaaa wasloadedfromanunauthorizedlibrary

DDN=dddddddd VOLSER=vvvvvv DSN=dsname

§ Linklist andLPAassumedauthorizedunlesscodedinJCL


EligibilityandRequirements(con’t)

§ RulesforloadmoduleresidenceforzIIP– LoadmoduleexecutedtostartCAIDMSCVmustresideininan

authorizedlibrary– CAIDMSnucleusmodulesmustbeloadedfromanauthorizedlibrary– IBMLElibrarymustbeauthorizedandintheCDMSLIBconcatenation– z/OSCallableServiceslibrarymustbeinlinklistorauthorizedand

includedinSTEPLIB– DBproceduresmustresideinanauthorizedlibrary


EligibilityandRequirements(con’t)

§ Individualnucleusmembersinaloadlibrarydonothavetobeauthorized– NoteveryloadlibraryinCAIDMSstartupSTEPLIB/CDMSLIBneedsto

beauthorized

§ Toensureallnucleusmodulesareloadedfromanauthorizedlibrary– AuthorizetheSMP/Etargetloadlibraryor– MaintaintwoseparatebutidenticalSMP/Etargetzonesor– ManuallycopyallmodulesintheSMP/Etargetloadlibrarytoan

authorizedlibrary


InformationalMessages

§ IfzIIP processorsarepresentandzIIP=NOisspecifiedortakenasthedefault– DisplayedontheJESlogveryearlyinthestartupprocess

+IDMSDC01610502zIIP processorsdetected.YoushouldconsiderusingZIIP=Y


UnitaskingorMultitasking

§ zIIPfeatureworkswithbothUnitaskingandMultitasking

§ Unitasking– 1EnclavestartedforthesingleTCB(SCA)tobeused

§ Multitasking– 1EnclavestartedforeachTCB(SCA)tobeused

§ Doesn’tdependuponthenumberofzIIPsinstalled§ If6subtasksarestartedformultitaskingandonly1zIIPengineisavailableonthemachine,6enclavesarestarted


ArchitectureChanges

§ MajorityofchangeslimitedtotheoperatingsystemdependentmoduleRHDCOESA

§ RoutinestoswitchbetweenTCBmodeandSRBmode– SRBmoderequiredtorunonazIIP– LimitationsonwhatcanrunonazIIP(inSRBmode)

§ Can’tdoI/OorSVCfunctionsforexample§ No“usermode”code

– CAADS,COBOL,Userwrittenexits,DBprocedures,etc

§ IDMSCOMP,IDMSDCOM,andPresspackdonotswapandwillruninSRBmode


ArchitectureChanges(con’t)

§ MostoftheCAIDMSsystemcodeiseligibletoruninSRBmodeanddoes– CodewhichisnoteligibletoruninSRBmodecallsroutinesinthe

operatingsystemdependentmoduleandrequestschangetoTCBmode

– RequestsaswapbacktoSRBmodeonceTCBmodeworkiscomplete

§ When“usermode”codeisbeingexecuted– TheCAIDMSsystemensurestheusermodecodeisruninTCBmode– When“usermode”codereturnstoSystemmodethe

CAIDMSsystemwillswapbacktoSRBmode


EvaluatingBenefitWithoutaPhysicalzIIPEngine

§ Notrecommended– Thisisachangefromearlierrecommendations– IfyouturnzIIPon(zIIP=YJCLstartupparm)andyoudonothaveazIIP

engine§ IDMSwillstillattempttoswapfromTCBmodetoSRBmodeandback§ TheresultsinadditionalCPUcyclestohandletheswappingwithnobenefit


EvaluatingBenefitWithoutaPhysicalzIIPEngine(con’t)

§ Besttoestimate– WhenIDMSisaBackendforaCICSFront-End

§ NoonlineUserprogramslikeCobol,ADS,etc– SomesiteshavereportedoffloadsofCPUcyclesinthe70to90+%range

§ OnlineUserprogramslikeCobol,ADS,etc– WillseealoweroffloadofCPUcyclesduetoswapping

– StillbeneficialsinceallIDMSSystemSupportCPUcyclesareeligibleforzIIPoffload

– IssueDCMTDSTATSYS§ LookatTotalSYSTEMCPUtime


RealWorldexampleofbenefitoffloadingcycles


RealWorldexampleofbenefitoffloadingcycles(con’t)

R17.0 R18.0 RO63129

TCBas%ofallCPU 25 50 02

SRBas% ofallCPU 75 50 98

%ofallCPUsenttozIIP 25 50 98

%ofsentzIIP runonzIIP 88 100 100

Swaps/task 1 .5 1.4

TCB(charged) cpu/task 0.0006048 0.0003516 0.0000115


RealWorldexampleofbenefitoffloadingcycles(con’t)

§ AllproductionV17CVsApril2009

§ $125K/yearreducedsoftwarecostsonV17

§ MultitaskingworkswellwithzIIPs

§ AllproductionV18CVsscheduledFebruary2012

§ $100K/yearadditionalreducedsoftwarecostsestimatedrunningV18


SectionSummary

§ Termsanddefinitions§ Benefits§ Operationalconsiderations§ zIIP exploitation§ ImplementingviaCAIDMSstartupparameters§ Architecturechanges§ Eligibilityandrequirements§ EvaluatingbenefitwithoutaphysicalzIIP engine§ RealWorldexampleofbenefitoffloadingcycles


Multi-TaskinginCAIDMS


SectionOverview

§ ThissessionfocusistheCAIDMSMultitaskingfeatureavailableforMVSandMVS-likeoperatingsystems.Topicscoveredincludeuse,monitoring,andtuning.


SectionTopics

§ WhatisMultitasking?

§ Considerations

§ Monitoring

§ Benefitsandcosts


WhatisMultitasking

§ DispatchinginaUnitaskingsystem

§ DispatchinginaMultitaskingsystem

§ Subtasks

§ Modes

§ RHDCMODE

§ CAIDMScomponentsinMPMODEANY


WhatisMultitasking(con’t)

§ DispatchinginaUnitaskingsystemCPU0

TASK3

#WAIT

TASK1

TASK2

#WAIT

CPU1 CPU2 CPU3 CPU4



§ DispatchinginaMultitaskingsystem

TASK6 #WAITTASK7

TASK3

TASK10

TASK8

#WAIT

TASK1 TASK2

#WAIT

TASK4

#WAITTASK9

TASK5

#WAIT

CPU0 CPU1 CPU2 CPU3 CPU4



§ Modes– ANY– DC– DB– USER– LOADER– DRIVER– CALLER

§ RHDCMODE(ModeManager)

§ Multitaskingis:– NotCPUdriven– Drivenbynumberoftasks

queuedforSystemServices(QueueDepth)



§ CAIDMSsystemcomponentsrunninginMPMODE=ANY– Dispatcher– Task-localfunctions– Storagemanager– Scratchmanager– Databaseengine– Securityengine


Considerations

§ ApplicationProgrammingconcerns– SharedStorage

§ SystemExits(RHDCUXIT)

§ DatabaseProcedures

§ ConsiderationsfortheDBA– Programdefinitionstatement

§ MPMODEis(ANYorSYSTEM)§ ProtectvsNoProtect§ Programpoolsizes

– Affinity(Subtask)– Invoking

§ FreeformJCLparameter– MT=Y,SUBT=n


BenefitsandCosts

§ Increasedthroughputandareductioninresponsetime

§ ThecostisaCPUincreasethatwillvaryfromsitetosite– Higherlevelofconcurrence– HandlingofMultiplesubtasks– RHDCMODE


SectionSummary

§ WhatisMultitasking?

§ Considerations

§ Monitoring

§ Benefitsandcosts


ParallelSysplexOptions


SectionOverview

§ ThissectiondiscussestheParallelSysplexfeaturesavailablewithCAIDMS.ThesefeaturesincludeSharedCache,DataSharing,DynamicRununitrouting,andCVcloning


SectionTopics

§ SharedCache

§ DataSharing

§ DynamicDatabaseSessionRouting

§ CVCloning


SharedCacheDefinition

§ Large,high-speedbufferinaCouplingFacility

§ ContainsdatabasepagesfromfilesassignedtothecacheandaccessedbytheCVsrunninginaSysplex

§ CornerstoneoftheCouplingFacilityfeatures

§ UsedbyAdvantage™CAIDMS®/DBDataSharingtoallowmultiplecentralversionstosimultaneouslyupdatethesamephysicaldatabase


SharedCacheImplementation

§ DefinesharedcachetotheCouplingFacility

STRUCTURENAME(IDMSSUPPCACHE002) SIZE(5120)PREFLIST(COUPLET1)


SharedCacheImplementation(con’t)

§ DMCLDefinition

ALTERDMCLR170DMCLINCLUDESEGMENTDBCRDEFAULTSHAREDCACHEIDMSSUPPCACHE002


SharedCacheImplementation(con’t)

§ DMCTVARYcommands

DCMTVARYSEGMENTNAMESHAREDCACHENAME/NODCMTVARYFILENAMESHAREDCACHENAME/NODCMTVARYAREANAMESHAREDCACHENAME/NODCMTVarySHAred CAche cache-nameON/OFf


SharedCacheTuningandMonitoring

§ Tuning– Increasesharedcachesize– Defineadditionalsharedcache

§ Monitoring– DCMT– AdvantageCAIDMSDatabasePerformanceMonitorOption– SREPORTS


DataSharingDefinition

§ Adatasharinggroup– NamedcollectionofAdvantageCAIDMS/DBsystemswithinasysplex– EachAdvantageCAIDMS/DBsystemassociatedwithadatasharing

groupisreferredtoasamemberofthatgroup

§ Datasharinganddatasharinggroupsarethemechanismsthatallowfilestobeopeninupdatemodebyalldesignatedcentralversions

§ Actualfiledataismaintainedinthesharedcachediscussedearlier


DataSharingImplementation

§ EachdatasharinggrouprequiresthedefinitionofaliststructureandalockstructureintheCouplingFacility

§ Oneormorecachestructuresmustbedefinedifthedatasharinggroupistoshareupdateaccesstodata

§ DefinitioninDMCL– Defaultdatasharingattribute– Segmentorfiledatasharingattribute


DataSharingImplementation(con’t)

§ Actuallistandlockstructuredefinitions:– STRUCTURENAME(CAIDMSSUPPGRP1LI)SIZE(4096)

PREFLIST(COUPLET1)– STRUCTURENAME(CAIDMSSUPPGRP1LK)SIZE(5120)

PREFLIST(COUPLET1)– SizesareinKbytes



§ DMCLdefinition:ALTERDMCLR170DMCLDATASHARINGDEFAULTSHAREDCACHEIDMSSUPPCACHE002

LOCKENTRIES100000MEMBERS5ONCONNECTIVITYLOSSNOABEND

INCLUDESEGMENTDBCR

DATASHARINGYES

DEFAULTSHAREDCACHEIDMSSUPPCACHE002



§ EachmemberofthedatasharinggrouprequiresSYSIDMSdefinitionwith:– DSGROUP– DCNAME

//SYSIDMSDD*DSGROUP=SUPPGRP1DCNAME=TECHD120


DataSharing

§ SystemManagedRebuild– ForplannedreconfigurationsoftheCouplingFacility

§ SystemManagedDuplexRebuild– ProvidesCouplingFacilityfailurerecoverycapability

§ Monitoring– DCMTcommands– AdvantageCAIDMSPerformanceMonitor– JREPORTS


CouplingFacilityStructures

§ AdvantageCAIDMSVisualDBA– Modelingtool– UsesCV’sDMCLdefinition– GeneratesCouplingFacility-readysyntaxfor:

§ Cache,List,andLockstructures


DataSharingBenefits

§ 24X7processing– FaultTolerance– SystemMaintenance

§ Scalability– AdditionalCVshaveupdateaccesstofiles

§ Workloadbalancing– AdditionalupdateCVscanbestartedandstoppedasneedschange;

workmaybeprocessedbyanyCVdefinedinthedatasharinggroup

§ Easytoimplementanduse


DynamicDatabaseSession- RoutingDefinition

§ ProvidesWorkloadbalancingbetweenAdvantageCAIDMS/DBsystemsrunningintheSysplex.

§ Workloadbalancingisdynamicandbasedonactualsystemload


DynamicDatabaseSession- RoutingImplementation

§ DBGROUPs

§ BackendDefinitions– AddDBGROUPstatement(s)toDatabaseNameTable– Use“CREATEDBGROUP”statementstoassigntheBackend(s)toa

DBGROUP(S)

CREATE DBGROUP R170DBTB.SPGROUP1 ENABLED



§ DBGROUPs

§ FrontendDefinitions– YoumustdefinetheDBGROUPasanodewithintheSYSGEN

ADD NODE SPGROUP1 GROUP DEFAULT NODE TECHD120

– YoucanoptionallymapaDBNAMEtoagroupbyusingtheVIA“GROUPNAME”parameteroftheResourceTablestatementwithinSYSGEN

MODIFY RESOURCE TABLEDBNAME IS DBCR VIA SPGROUP1



§ CouplingFacilityconsiderations– DefineaCouplingFacilitystructurefor

eachDBGroup definedtoAdvantageCAIDMS/DB

– PrefixDBGroup namewith"CAIDMS”– SizeisinKbytes– Example:

STRUCTURE NAME(CAIDMSSPGROUP1) SIZE(512PREFLIST(COUPLET1)



§ Workwillbedynamicallyroutedwhenoneorbothofthefollowingaretrue:– TheDBNODEusedisdefinedasagroupviatheNODEstatementof

SYSGEN– TheDBNAMEusedisdefinedintheResourceTableasaGroup

§ TheDBNAMEand/ortheDBNODEaresetby– Theapplication– ViaaDCUFSETcommand– ViaEXIT23



TITLE'EXIT23- PREBINDEXIT‘XIT23 #MOPTENV=SYS,AMODE=31,RMODE=ANYXIT23 CSECTXIT23EP1 #STARTMPMODE=ANY

USINGCSA,R10LR2,4(,R1)40BYTEDATAAREAUSINGPARMAREA,R2CLCPSSCNAME(4),=CL4'DBCR'ISTHISFORDBCRBNERETURNNO!JUSTEXITMVCPDBNODE,=CL8'SPGROUP1'OVERRIDEDBNODE

*** MVCPDBNAME,=CL8'DBCR'orOVERRIDEDBNAMERETURN#RTNRETURNTOCALLER

LTORG



COPY#CSADS

PARMAREADSECT

PSSCNAMEDSCL8SSCNAME

PDBNODEDSCL8DATABASENODE

PDBNAMEDSCL8DATABASENAME

PDICNODDSCL8DICTIONARYNODE

PDICNAMDSCL8DICTIONARYNAME

END



§ Monitoring– DCMTcommands– LOOK– AdvantageCAIDMSPerformanceMonitor’sIntervalComponent(online

andBatch)


DynamicDatabaseSession– RoutingBenefits


§ Scalability– AdditionalCVshaveupdateaccesstofileswhenusedwithdatasharing

§ Dynamicworkloadbalancing– AdditionalCVscanbestartedandstoppedasneedschange;workis

routedtootherCVsdefinedintheDBGroup

§ Easytoimplementanduse


CVCloningDefinition

§ AllowsyoutostartmultipleCVsthatarecopies(clones)ofanexistingAdvantageCAIDMS/DBsystem

§ Systemdefinitionandfiles– Samephysicalentitiesasthesystembeingclonedwithafewexceptions


CVCloningNamingConventions

§ CVNumber,DCSystemNumber,VTAMAPPLID,andSystemNodeNameforaCVmustconformtospecificnamingconventions

§ Byadheringtothesenamingconventions,AdvantageCAIDMS/DBcanimplementcloneswithoutgeneratingmultiplephysicalcopiesofasystemdefinition


CVCloningNamingConventions(con’t)

§ DCsystemnumbermustmatchCVnumber

§ Mustbeinrangeof0through255

§ AllVTAMApplids mustfollowtheconventionofxxxxxnnn– xxxxx canbeanyfivecharacters– nnn isthesysgenned CVnumberandisoverlaidatruntimewiththe

numberdeterminedduringstartupoftheclonedCV


CVCloningNamingConventions(con’t)

§ AdvantageCAIDMS/DBsystemnodenamesmustfollowtheconventionofyyyyynnn– wherethefirstfivecharacters(i.e.,yyyyy)canbeanycharactersyou

needtomakethenameuniquewithinyourenvironment– nnn isthenumberspecifiedfortheCVatsystemgeneration

SYSGEN17.0ONLINEPAGE1LINE1DICT=SYSTEMADDSYSTEM120SYSTEMIDISTECHD120CVNUMBERIS120ADDLINEVTAMAPPLICATIONIDISA31II120


CVCloning

§ SpecialFileRequirements– EachclonedCVrequiresitsowncopyofthefollowingfiles:

DDLDCLOG,DDLDCSCR,DDLDCQUE,AllJournals


CVCloning(con’t)

§ Usethe“CLON=“and“CLONES=“parameterintheJCLparmfortheIDMSsystemstartup.

//R170DC99EXECPGM=IDMSDC99,REGION=0K,TIME=1440,//PARM='S=110,CLON=Y,CLONES=9”

§ Whenusedinadatasharinggroup,aclonemayhaveupdateaccesstoalldatabasefiles


CloningBenefits


§ Scalability– AdditionalCVshaveupdateaccesstofileswhenusedwithdatasharing

§ Dynamicworkloadbalancing– AdditionalCVscanbestartedandstoppedasneedschange;workis

routedtootherCVsdefinedintheDBGroup§ EasywaytoaddadditionalCVs§ NoadditionalsystemdefinitionsfortheDBAtomaintain


SectionSummary

§ SharedCache

§ DataSharing

§ DynamicDatabaseSessionRouting

§ CVCloning

@CAWORLD#CAWORLD ©2016CA.AllRIGHTSRESERVED.112 @CAWORLD#CAWORLD

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CA IDMS Deadlock Analysis

Technology