CICS Transaction Server for z/os. CICS DB2 Guide. Version 3 Release 1 SC

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CICS

Transaction

Server

for

z/OS

CICS

DB2

Guide

Version

3 Release

1

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CICS

Transaction

Server

for

z/OS

CICS

DB2

Guide

Version

3 Release

1

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Note!

Beforeusingthisinformationandtheproductitsupports,besuretoreadthegeneralinformationunder“Notices”onpage 213.

Secondedition(September2006)

ThiseditionappliestoVersion 3 Release 1ofCICSTransactionServerforz/OS,programnumber5655-M15,and toallsubsequentversions,releases,andmodificationsuntilotherwiseindicatedinneweditions.Makesureyouare usingthecorrecteditionfortheleveloftheproduct.

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Environment. . . 34 Syntax . . . 34 Abbreviation . . . 34 Authorization. . . 34 Parameterdescription . . . 35 Usage note . . . 35 Example . . . 35 DSNC DISCONNECT . . . 36 Environment. . . 36 Syntax . . . 36 Abbreviation . . . 36 Authorization. . . 36 Parameterdescription . . . 36 Usage notes. . . 36 Example . . . 37 DSNC DISPLAY . . . 38 Environment. . . 38 Syntax . . . 38 Abbreviation . . . 38 Authorization. . . 38 Parameterdescription . . . 38 Parameterdescription . . . 38 Parameterdescription . . . 39 Usage notes. . . 39

DISPLAYPLANorTRAN . . . 39

DISPLAYSTATISTICS output . . . 40

DSNC MODIFY. . . 43 Environment. . . 43 Syntax . . . 43 Abbreviation . . . 43 Authorization. . . 43 Parameterdescription . . . 43 Usage notes. . . 44 Examples . . . 44 DSNC STOP . . . 46 Environment. . . 46 Syntax . . . 46 Abbreviation . . . 46 Authorization. . . 46 Parameterdescription . . . 46 Usage notes. . . 46 Examples . . . 47 DSNC STRT. . . 48 Environment. . . 48 Syntax . . . 48 Abbreviation . . . 48 Authorization. . . 48 Parameterdescription . . . 48 Usage notes. . . 48 Examples . . . 49

Chapter5. Definingthe CICSDB2connection . . . 51

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Whathappens duringSQLprocessing . . . 53 Thread creation. . . 54 SQLprocessing . . . 54 Commitprocessing . . . 54 Thread release . . . 55 Thread termination . . . 55

Howthreadsarecreated,used,andterminated. . . 55

Protectedentry threads. . . 57

Unprotectedentrythreadsfor criticaltransactions . . . 58

Unprotectedentrythreadsfor backgroundtransactions . . . 59

Poolthreads. . . 59

Selectingthreadtypesfor optimumperformance . . . 60

SelectingBINDoptionsforoptimum performance . . . 62

CoordinatingyourDB2CONN, DB2ENTRY,andBINDoptions . . . 62

Chapter6. SecurityinaCICSDB2environment . . . 65

Controllingusers’accessto DB2–relatedresourcesinCICS(CICSDB2 transactions,resourcedefinitions,andattachmentfacilitycommands) . . . . 66

Controllingusers’accessto DB2CONN,DB2TRAN,andDB2ENTRY resource definitions . . . 67

Using resourcesecurityto controlaccessto DB2ENTRYandDB2TRAN resource definitions . . . 68

Using commandsecuritytocontroltheissuingofSPIcommandsagainst DB2CONN, DB2ENTRY,andDB2TRANresourcedefinitions . . . 69

Using surrogatesecurityandAUTHTYPEsecuritytocontrolaccesstothe authorizationIDsthatCICSprovidestoDB2 . . . 71

Controllingusers’accessto DB2-relatedCICStransactions . . . 73

Providing authorizationIDs toDB2for theCICSregionandforCICS transactions . . . 74

Providing authorizationIDs toDB2for aCICSregion. . . 75

Providing aprimaryauthorizationIDforaCICSregion . . . 75

Providing secondaryauthorizationIDs fora CICSregion . . . 76

Providing authorizationIDs toDB2for CICStransactions . . . 77

Providing aprimaryauthorizationIDforCICStransactions. . . 78

Providing secondaryauthorizationIDs forCICStransactions . . . 80

AuthorizinguserstoaccessresourceswithinDB2(DB2commands,plans,and dynamicSQL) . . . 82

Controllingusers’accessto DB2commands . . . 83

Controllingusers’accessto plans . . . 84

Chapter7.Application designanddevelopment considerationsforCICS DB2 . . . 87

DesigningtherelationshipbetweenCICSapplicationsandDB2plansand packages . . . 88

Asampleapplication. . . 89

Using packages . . . 90

Using onelargeplanfor alltransactions . . . 93

Using manysmallplans . . . 94

Using plansbasedontransactiongrouping . . . 95

Dynamic planexits . . . 96

If youneedto createplansforanapplicationthathas alreadybeen developed. . . 99

If youneedto switchplanswithinatransaction . . . 99

Dynamic planswitching . . . 100

Switchingtransaction IDsinordertoswitchplans . . . 100

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SQL, threadsafeandotherprogrammingconsiderations forCICSDB2

applications. . . 105

Enabling CICSDB2applicationsto exploittheopentransactionenvironment (OTE)throughthreadsafeprogramming . . . 106

SQLlanguage. . . 109

Using qualifiedandunqualified SQL . . . 109

Views . . . 110

Updatingindexcolumns . . . 110

Dependencyof uniqueindexes . . . 110

Commitprocessing . . . 111

Serializingtransactions . . . 111

Pagecontention . . . 112

CICSandCURSORWITHHOLDoption . . . 113

EXECCICSRETURNIMMEDIATEcommand . . . 114

AvoidingAEY9abends . . . 114

Chapter8. UsingJDBCandSQLJtoaccessDB2datafrom Java programsandenterprisebeans writtenforCICS . . . 117

Making JDBCandSQLJworkintheCICSDB2environment . . . 117

Requirements tosupportJavaprogramsintheCICSDB2environment. . . . 119

ProgrammingwithJDBCandSQLJintheCICSDB2 environment . . . 121

Acquiring aconnection toadatabase . . . 122

Howmanyconnectionscanyouhave? . . . 123

Acquiring aconnection usingtheJDBCDriverManagerinterface . . . 123

Acquiring aconnection usingtheDataSourceinterface. . . 124

Settingupthesample applicationstopublish,lookupandretracta DataSource. . . 125

Publishinga DataSourceusingCICSDataSourcePublish.java . . . 126

Looking upa DataSourceusingCICSjdbcDataSource.java . . . 127

Retracting aDataSourceusingCICSDataSourceRetract.java . . . 128

Committingaunit ofwork . . . 129

Autocommit. . . 129

Syncpointissues forexplicitanddefaultURLs . . . 130

CICSabendsduringJDBCorSQLJ requests . . . 130

Using JDBCandSQLJinenterprisebeans:specialconsiderations . . . 130

Chapter9. PreparingCICSDB2programsforexecutionandproduction 133 TheCICSDB2testenvironment . . . 133

CICSDB2programpreparationsteps . . . 134

CICSSQLCAformattingroutine . . . 136

Whatto bindafteraprogramchange . . . 137

Bindoptions andconsiderationsfor programs . . . 138

RETAIN . . . 138

Isolationlevel . . . 139

Planvalidation time. . . 139

ACQUIRE andRELEASE . . . 139

CICSDB2programtestinganddebugging . . . 139

Goingintoproduction: checklistforCICSDB2applications . . . 139

Tuning aCICSapplicationthataccesses DB2 . . . 142

Chapter10.Accounting andmonitoringin aCICSDB2environment 145 CICS-supplied accountingandmonitoringinformation . . . 145

DB2-suppliedaccounting andmonitoringinformation . . . 146

Monitoringa CICSDB2environment:Overview . . . 147

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MonitoringtheCICSDB2attachmentfacilityusingCICSDB2attachment

facilitycommands . . . 148

MonitoringtheCICSDB2attachmentfacilityusingDB2commands . . . . 148

MonitoringtheCICSDB2attachmentfacilityusingCICSDB2statistics 148 MonitoringCICStransactionsthataccessDB2resources. . . 151

MonitoringDB2whenused withCICS . . . 152

MonitoringDB2usingtheDB2statisticsfacility . . . 153

MonitoringDB2usingtheDB2accountingfacility. . . 155

MonitoringDB2usingtheDB2performancefacility . . . 155

MonitoringtheCICSsysteminaCICSDB2environment . . . 156

AccountinginaCICSDB2environment:Overview . . . 156

Accountinginformationprovided bytheDB2 accountingfacility. . . 157

DatatypesinDB2accounting records. . . 158

DB2accounting reports . . . 160

RelatingDB2accounting recordstoCICSperformanceclassrecords . . . . 161

WhataretheissueswhenmatchingDB2accountingrecordsandCICS performancerecords? . . . 162

ControllingtherelationshipbetweenDB2accountingrecordsandCICS performanceclassrecords . . . 162

Using dataintheDB2accounting recordtoidentify thecorrespondingCICS performanceclassrecords . . . 163

Strategies youcanuseto matchDB2accounting recordsandCICS performanceclassrecordsandchargeresourcesbackto theenduser . . 164

Accountingfor processorusageinaCICSDB2environment . . . 167

AccountingCLASS1 processortime . . . 172

AccountingCLASS2 processortime . . . 173

CalculatingCICSandDB2processortimesforDB2Version5or earlier 174 CalculatingCICSandDB2processortimesforDB2Version6or later 174 Chapter11.ProblemdeterminationforCICSDB2 . . . 177

Thread TCBs(taskcontrolblocks) . . . 177

Wait typesforCICSDB2. . . 178

Messages forCICSDB2. . . 182

Tracefor CICSDB2 . . . 182

CSUBtrace . . . 191

Dumpfor CICSDB2 . . . 193

DB2 threadidentification . . . 194

TransactionabendcodesforCICSDB2 . . . 194

ExecutionDiagnosticFacility(EDF)for CICSDB2 . . . 195

Handlingdeadlocks intheCICSDB2environment . . . 196

Two deadlocktypes. . . 197

Deadlock detection . . . 197

Findingtheresourcesinvolved . . . 198

FindingtheSQLstatementsinvolved . . . 198

Findingtheaccesspathused . . . 198

Determiningwhythedeadlockoccurred . . . 198

Making changes . . . 198

Bibliography . . . 201

TheCICSTransactionServerfor z/OSlibrary . . . 201

Theentitlementset . . . 201

PDF-only books . . . 201

Other CICSbooks . . . 203

Booksfromrelatedlibraries. . . 203

DB2 . . . 203

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ResourceManagement Facility(RMF). . . 204

Determiningif apublicationiscurrent . . . 204

Accessibility . . . 205

Index . . . 207

Notices . . . 213

Programminginterface information . . . 214

Trademarks. . . 214

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Preface

What

this

book

is

about

This bookisforanyonewho uses,orisconsideringusing,theCICS®Transaction Serverfor z/OS®, Version3Release1DB2®interface.Itisintendedto beusedin conjunctionwithexistingmanualsintheCICSandDB2libraries.Thesearereferred to whereappropriate.

Theaimof thisbookisto giveintroductoryandguidanceinformationonevaluating, installing, andusingtheCICSDB2attachmentfacility,andondefining and

maintainingyourCICSDB2environment.

What

you

need

to

know

to

understand

this

book

Before youreadthisbook,you needageneralunderstandingofCICS.Youcanfind generalintroductoryinformation intheCICSFamily:GeneralInformation.You should alsohavesomeknowledgeof theconceptsofdatamanagement and databases. Forguidanceonthesetopics,seetheDB2Universal Database™for OS/390®andz/OSAdministrationGuide.

Notes

on

terminology

When theterm“CICS”isusedwithout anyqualification,itrefers totheCICS element ofIBM®CICSTransactionServerfor z/OS.

“DB2”without anyqualificationrefersto DB2UniversalDatabaseServerfor OS/390 andz/OS.

CICSPlex® SMisusedfor CICSPlexSystemManager.

“MVS™”isusedfor theoperating system,which canbeanelementof z/OS, OS/390,or MVS/EnterpriseSystemArchitectureSystemProduct(MVS/ESA™SP).

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Summary

of

changes

This bookisbasedontheCICSDB2GuideforCICSTransactionServerfor z/OS, Version2 Release3.Changesfromthateditionaremarkedbyverticalbars inthe leftmargin.

This partlistsbrieflythechangesthathave beenmade forthefollowingreleases: For mostitemsineachof thelistsabove,thereisalink tothepartofthebook wherethereismoredetail.

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

3 Release

1

Themoresignificantchangesfor thiseditionare: Technicalchanges

v

Becauseof theremoval ofrun-timesupportforJavaprogramobjectsand

hot-pooling(HPJ),informationabout usingthis typeofJavaprogramtoaccess DB2isremovedfromChapter8, “UsingJDBCandSQLJto accessDB2 data fromJavaprograms andenterprisebeanswrittenforCICS,”onpage117.Ifyou haveanyJavaprogramobjectsthataccessDB2,andneedto migratethem to runinaJVM,“Requirements tosupportJavaprogramsintheCICSDB2 environment”onpage119hasinformationontherequirements forJava programsthatrunina JVMandaccessDB2.

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

2 Release

3

Themoresignificantchangesfor thiseditionare: Technicalchanges

v Therearechangestothesamplesthatareprovided tosetupa

CICS-compatibleDataSource.Chapter8,“UsingJDBCandSQLJ toaccessDB2 datafromJavaprograms andenterprisebeanswrittenforCICS,”onpage117 hasinformationonusingtheDataSourceinterface toacquireconnections.

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

2 Release

2

Themoresignificantchangesfor thiseditionare:

Technicalchanges:Opentransactionenvironment(OTE)exploitation v

IfyourCICSsystemisconnectedto DB2Version6orlater, CICSnow exploits

theopentransactionenvironment(OTE)to improveperformancebyreducing TCBswitching.For fulldetailsof theCICSDB2configurationneededtoexploit theopentransactionenvironment,see“Migratingto adifferentreleaseofDB2” onpage 15.

v Foranoverviewoftheeffectsofthis change,seetheCICSTransactionServer

forz/OS ReleaseGuidefor CICSTransactionServerforz/OS, Version2Release 2.Chapter1,“Overview oftheCICSDB2interface,”onpage1, hasexplanations oftheimportantdifferencesinthewayCICSconnectsto DB2intheopen transactionenvironment,includingtheuseof openTCBsinstead ofsubtask TCBsto runthreads(see“Overview:Howthreadswork”onpage2). “Thread TCBs(task controlblocks)”onpage177hasfurtherinformationonopenTCBs beingused asthreadTCBs,andonthenewmodulesusedto controlCICSDB2

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connectionprocessing.“Howthreadsarecreated,used,andterminated”onpage 55explainsthedifferencesinthreadusewhenusingopenTCBs.

v Whenusingtheopentransactionenvironment,to besurethatyouhaveenough

openTCBsavailableto processyourDB2workload,ensurethatthelimitsetin yourMAXOPENTCBSsysteminitializationparameter isgreater thanthelimitset intheTCBLIMITattributeofyour DB2CONNdefinition.Formoreinformation,see “TheMAXOPENTCBSsystem initializationparameterandTCBLIMIT”onpage 52.

v

Togaintheperformancebenefitsof theopen transactionenvironment,

applicationprograms mustbethreadsafe.See“EnablingCICSDB2applications toexploit theopen transactionenvironment(OTE)throughthreadsafe

programming”onpage106forinformation.

v OTEexploitationisparticularlyimportant forenterprisebeansthatmakeDB2

requests.See“UsingJDBCandSQLJ inenterprisebeans:special considerations”onpage130for information.

v Thereisanew waittypefor theopentransactionenvironment,CDB2CONN,and

someof theexistingwaittypesonlyapplywhenCICSisnotusingtheopen transactionenvironment(whenit isconnectedto DB2Version5or earlier).See “WaittypesforCICSDB2”onpage178for information.

v

Theuseoftheopentransaction environmentaffectshowyoucanpurge CICS

DB2transactions.See“PurgingCICSDB2transactions”onpage30for information.

v TherearedifferencestothetracingperformedfortheCICSDB2attachment

facilityintheopentransactionenvironment.Amongother things,theCICSDB2 connectionprogramDFHD2D2,whichreplacesDFHD2EX3intheopen

transactionenvironment,makesnewentriesintheCSUBtracetable.See“Trace forCICSDB2”onpage182forinformation.

v Therearechangesto accountingandperformancemonitoringasaresultof the

availabilityoftheopentransaction environment.SeeChapter10,“Accounting andmonitoringina CICSDB2environment,” onpage145forinformation. Technicalchanges:Groupattach

v

IfyourCICSsystemisconnectedto DB2Version7orlater, youcannowuse the

DB2groupattachfacility,whichallowsCICSto connectto anyonememberof a datasharinggroupof DB2subsystems,ratherthanto aspecificDB2subsystem. Forfulldetails oftheCICSDB2configurationneededto usetheDB2group attachfacility,see“Migratingtoa differentrelease ofDB2”onpage15.

v See“UsingtheDB2groupattachfacility”onpage51formoreinformationabout

thegroupattachfacility.GroupattachiscontrolledbythenewDB2GROUPID andRESYNCMEMBERattributesof theDB2CONNdefinition—seetheCICS ResourceDefinitionGuidefor fulldescriptionsoftheseattributes.If youareusing groupattach,thisaffectstheresolutionofindoubtunitsofwork,andyouneedto decideonthestrategy thatCICSadopts—see“Resolvingindoubtunitsofwork (UOWs)”onpage26for details.

v Ifyouareusinggroupattach,theoutputfrom,anduseof,theDSNCSTRT

commandisaffected—see“DSNC STRT”onpage48for information.Ifyou specifya DB2IDona DSNCSTRTcommand,thisoverridesandblanks outa DB2GROUPIDsetintheinstalledDB2CONNdefinition.Youcannotspecifya DB2GROUPIDona DSNCSTRTcommand.

Othertechnicalchanges

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providedbyDB2,thatsupports aselectedsubsetoftheJDBC2.0API,including supportfortheDataSourceinterface.ADataSourceisanalternativewayof obtainingaJDBCconnectionto adatabase.Chapter8, “UsingJDBCandSQLJ toaccessDB2datafromJavaprogramsandenterprisebeanswrittenfor CICS,” onpage 117hasinformationontherequirementsfor theJDBC2.0driver,andon usingtheDataSourceinterface toacquireconnections.Samples areprovided to setupa CICS-compatibleDataSource.

v Inthis releaseofCICS,PLANandPLANEXITNAMEoptionsareaddedto the

INQUIREDB2TRANcommand,soyoucanfindoutina singlestepwhichplan is usedbyaspecifiedtransaction orsetoftransactions,orwhich transactionsuse aspecifiedplan. SeetheCICSSystemProgrammingReference forinformation. v TheoutputfromtheDSNCDISPLAYPLANorTRANcommandnow

distinguishesbetweenathread thatisactiveandcurrently executinginDB2, and athread thatisactivebutisnotcurrentlyexecutinginDB2.See“DSNC

DISPLAY”onpage38for information.

v WhenpreparingCICSprogramsthataccessDB2,youcannow useLanguage

Environment-conforminglanguagecompilers(COBOLandPL/I)thatsupportthe integratedCICStranslator and,dependingonyourreleaseof DB2,anSQL statementcoprocessor.See“CICSDB2programpreparationsteps”onpage134 formoreinformationonthechangesto theprogrampreparationprocess.

Structuralchanges

v Chapter1, “Overviewof theCICSDB2interface,”onpage 1,hasbeenrewritten,

andnowincludesinformationon – howthreadsandthreadTCBswork

– howtheDB2CONN,DB2ENTRYandDB2TRANdefinitions worktogether

– howplans,packagesanddynamicplanexitswork

v Chapter7, “Applicationdesignanddevelopmentconsiderationsfor CICSDB2,”

onpage 87andChapter9,“PreparingCICSDB2programsfor executionand production,”onpage133havebeenreorganised. Inparticular,Chapter8, “Using JDBCandSQLJto accessDB2data fromJavaprogramsandenterprisebeans writtenforCICS,”onpage117isnowa separatechapter.

v Chapter2, “Installationandmigrationnotesfor CICSDB2,”onpage 15and

Chapter5, “DefiningtheCICSDB2connection,”onpage 51have been reorganised.

v Thechapter’Customization:dynamicplanexits’hasbeenremoved, andthe

informationitcontainedisnowin“Dynamicplan exits”onpage96and“Dynamic planswitching”onpage 100.

v Thechapter’Monitoring,tuningandhandlingdeadlocks’hasbeenremoved.The

informationitcontainedisnowinChapter10,“Accountingandmonitoringina CICSDB2environment,”onpage145,Chapter9,“PreparingCICSDB2 programsfor executionandproduction,”onpage133, Chapter11,“Problem determinationforCICSDB2,”onpage177,andtheCICSPerformanceGuide.

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

2 Release

1

Themoresignificantchangesfor thiseditionare:

v Informationisprovided onsupportfor Javaprograms forCICSandenterprise

beansaccessingDB2(see“Requirementsto supportJavaprograms intheCICS DB2environment”onpage119and“UsingJDBCandSQLJ inenterprisebeans: specialconsiderations” onpage130.“Dynamicplanexits”onpage96explains theconsequencesof thesechangesfordynamicplanexits.

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v Informationhasbeenaddedona saferwaytopurgeCICSDB2transactions

usingtheDB2 CANCELTHREADcommand(see“PurgingCICSDB2 transactions”onpage30and“Waittypesfor CICSDB2”onpage178).

v InformationhasbeenaddedonDB2thread identificationbyacorrelationID(see

“DB2threadidentification” onpage194andthenotein“DSNCDISPLAY”on page38).

v

Furtherinformationonthechangesto theINITPARM systeminitialization

parameterhasbeenaddedto “EffectofmigrationtoRDOontheINITPARM systeminitialization parameter”onpage 21and“DSNC STRT”onpage48. v In“MigratingRCTsto theCSDusingDFHCSDUP”onpage23,anotehasbeen

addedabout theeffectonCICSDB2 statisticswhenyouusewildcardcharacters indefiningtransactionIDs.

v Anewparameter,CPRMAPPL,containing the8 bytecharactername ofthe

applicationprogramissuinganSQLrequest,isnowpassedto thesample dynamicplanexitDSNCUEXT—see“Dynamicplan exits”onpage96,table Table4onpage97.

v In“Wait typesfor CICSDB2”onpage 178,informationisgivenonanew wait

addedto DFHD2EX2,to waituntil theTERM processiscomplete(seeTable15 onpage182).

For mostitemsineachof thelistsabove,thereisareferenceto thepartof the book wherethereismoredetail.

Earlier

releases

Changes forCICSTransactionServerforOS/390Version1Release3

Major changesfor thiseditionprovideinformationonthechangesto theINITPARM system initializationparameternow thatCICSnolongersupportsrunningtheCICS DB2 attachmentfacilitywithamacroRCT.See“Effectof migrationto RDOonthe INITPARM systeminitialization parameter”onpage 21and“MigratingtoRDOfor DB2 resourcedefinition”onpage 21.

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Chapter

1. Overview

of

the

CICS

DB2

interface

This chaptergivesanoverviewof theCICSinterface toDB2(Database2™_).

This chapterincludesthefollowingtopics: v “Overview:HowCICSconnectstoDB2”

v “Overview:Howthreadswork”onpage 2

v “Overview:Howyoucan definetheCICSDB2connection”onpage8

v “Overview:Enabling CICSapplicationprogramsto accessDB2”onpage10

Overview:

How

CICS

connects

to

DB2

ACICSDB2attachmentfacilityisprovidedwithCICS.TheCICSDB2attachment facilityprovidesCICSapplicationswithaccessto DB2datawhileoperating inthe CICSenvironment.CICSapplications, therefore,canaccessbothDB2data and CICSdata.CICScoordinates recoveryofbothDB2 andCICSdataif transactionor system failureoccurs.

TheCICSDB2attachmentfacilitycreatesanoverallconnection betweenCICSand DB2. CICSapplicationsuse thisconnectionto issuecommandsandrequeststo DB2.Theconnection betweenCICSandDB2canbecreatedorterminatedatany time, andCICSandDB2 canbestartedandstoppedindependently.Youcan name anindividualDB2 subsystemtowhich CICSconnects, or(ifyouhave DB2Version 7 orlater)youcanusethegroupattachfacilitytoletDB2chooseanyactive memberof adata-sharinggroupof DB2subsystemsfor theconnection.Youalso have theoptionof CICSautomaticallyconnectingandreconnectingtoDB2.ADB2 system canbesharedbyseveralCICSsystems,buteachCICSsystemcan be connectedto onlyoneDB2subsystemata time.

Attachmentcommandsdisplayandcontrolthestatusof theCICSDB2attachment facility,andareissuedusingtheCICSsuppliedtransactionDSNC.Theattachment commands are:

v STRT-starttheconnection toDB2

v STOP-stoptheconnectionto DB2

v DISP-displaythestatusofthreads,anddisplaystatistics

v MODI-modifycharacteristicsoftheconnectionto DB2

v DISC-disconnectthreads

Theconnection betweenCICSandDB2isamultithreadconnection.Withinthe overallconnection betweenCICSandDB2,thereisa thread—anindividual connection intoDB2—foreach activeCICStransactionaccessingDB2.Threads allow eachCICStransactiontoaccessDB2resources,suchasa command processororanapplicationplan(theinformationthattellsDB2whattheapplication program’sSQLrequests are,andthemost efficientwaytoservicethem). See “Overview:Howthreadswork”onpage2 belowforafullexplanationofhow threadswork.

When anapplicationprogramoperating intheCICSenvironmentissues itsfirst SQLrequest,CICSandDB2processtherequestasfollows:

v Alanguageinterface,orstub, DSNCLI,thatislink-editedwiththeapplication

programcallstheCICSresourcemanagerinterface (RMI).

v TheRMIprocessestherequest,andpassescontrolto theCICSDB2attachment

facility’stask-relateduserexit (TRUE),themodulethatinvokesDB2foreach task.

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v TheCICSDB2 attachmentfacilityschedulesa threadfor thetransaction.Atthis

stage,DB2checksauthorization,andlocates thecorrectapplicationplan. v DB2takescontrol,andtheCICSDB2attachmentfacilitywaitswhileDB2

servicestherequest.

v WhentheSQLrequestcompletes,DB2 passestherequesteddatabacktothe

CICSDB2attachmentfacility.

v CICSnowregainscontrol,andtheCICSDB2attachmentfacilitypasses thedata

andreturnscontrolto theCICSapplicationprogram.

The

DB2

address

spaces

DB2 requiresseveraldifferentaddressspaces.Figure1shows theseaddress spaces.

Varioustasksareperformedinthedifferentaddressspaces,asfollows: DSN1MSTR

for systemservicesthatperformavarietyofsystem-related functions. DSN1DBM1

for databaseservicesthatmanipulatemost ofthestructuresinuser-created databases.

DSN1DIST

for distributeddatafacilitiesthatprovidesupportfor remoterequests. IRLMPROC

for theinternalresourcelockmanager(IRLM),which controlsDB2locking. DSN1SPAS

for storedprocedures,which provideanisolatedexecutionenvironmentfor user-written SQL.

Overview:

How

threads

work

WithintheoverallconnectionbetweenCICSandDB2, eachCICStransactionthat accesses DB2needsathread,anindividual connectionintoDB2.Threadsare createdwhentheyareneededbytransactions,atthepointwhentheapplication

DSN1SPAS address space IRLMPROC address space DSN1DIST address space DSN1DBM1 address space CICS Connections DB2 Subsystem CICS address space DSN1MSTR address space

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resourcesmanagedbyDB2. Whenathreadisnolongerneededbythetransaction, becausethetransactionhasaccessedalltheresourcesitneedstouse, thethread isreleased (typicallyaftersyncpointcompletion).It takesprocessorresourcesto createathread,sowhena threadisreleased,theCICSDB2attachmentfacility checkstosee ifanothertransactionneedsathread.Ifanothertransactioniswaiting for athread,theCICSDB2attachmentfacilityreusestheexistingthread forthat transaction toaccessDB2.Ifthethreadisnolongerneededbyanytransaction, it isterminated,unlessyouhave requestedthatit shouldbeprotected(kept)for a periodoftime.Aprotected threadisreusedifanothertransactionrequestsit within thatperiodoftime; ifnot,it isterminatedwhentheprotectiontime expires.

There aredifferenttypesofthread,andyoucansetalimitonthenumberofeach type ofthread thatcanbeactiveat anyonetime.Thisprevents theoverall CICS DB2 connectionfrombecomingoverloadedwithwork.Aspecialtypeof threadis used forDB2commands issuedusingtheDSNC transaction,andyoucanalso definespecialthreadsforCICStransactionswithparticularrequirements,suchas transactionsthatrequireafastresponsetime.Youcandefinewhata transaction must doif nomorethreadsofthetypeit needsareavailable—itcanwaituntil a thread oftherighttypeisavailable;it canuseageneral-purposethread,calleda pool thread;or itcanabend.

Thetypesofthread providedbytheCICSDB2attachmentfacilityare: Command threads

CommandthreadsarereservedbytheCICSDB2attachmentfacilityfor issuingcommandsto DB2usingtheDSNC transaction.Theyarenotused for commandsactingontheCICSDB2attachmentfacilityitself,because thesecommandsarenotpassed toDB2.When acommandthreadisnot available, commandsautomaticallyoverflowtothepool,andusea pool thread.Commandthreadsaredefinedinthecommandthreadssection of theDB2CONNdefinition.

Entry threads

Entrythreadsarespeciallydefinedthreadsintendedfor transactionswith specialrequirements,suchastransactionsthatrequireafastresponse time, ortransactionswithspecialaccountingneeds.Youcaninstructthe CICSDB2attachmentfacilitytogive entrythreadstoparticularCICS transactions.Youdefinethedifferenttypesof entrythreadsthatareneeded for differenttransactions,andyoucan setalimitonthenumberofeachof thesetypesofentrythread.Ifa transactionispermittedtouseanentry thread,butnosuitableentrythread isavailable, thetransaction can overflowtothepool anduse apoolthread,orwaitforasuitableentry thread,orabend,asyouhavechoseninthedefinitionfortheentrythread. Acertainnumberof eachtypeof entrythreadcanbeprotected.Whenan entry threadisreleased,if itisprotectedit isnotterminatedimmediately.It iskeptfor aperiodoftime, andifanotherCICStransaction needsthesame type ofentrythread duringthatperiod,itisreused.Thisavoidsthe

overhead involvedincreatingandterminatingthethread foreach

transaction.Anentrythread thatisunprotectedisterminatedimmediately, unless aCICStransactioniswaitingto useitthemomentitisreleased. EntrythreadsaredefinedusingaDB2ENTRYdefinition.

Pool threads

Poolthreadsareusedfor alltransactionsandcommandsthatarenotusing anentrythread oraDB2commandthread.Poolthreadsareintendedfor low volumetransactions,andforoverflowtransactionsthatcouldnotobtain

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anentrythread oraDB2commandthread.Apoolthread isterminated immediatelyif noCICStransactioniswaitingtouseit.Poolthreadsare definedinthepoolthreadssectionof theDB2CONNdefinition.

For moredetailedinformationonhowthedifferenttypesofthread arecreated,used andterminated,see“Howthreadsarecreated,used,andterminated”onpage55. Each threadrunsundera threadtaskcontrolblock(threadTCB)thatbelongs to CICS.CICSandDB2bothhave connectioncontrolblockslinkedto thethreadTCB. They usetheseconnection controlblocksto managethethread intoDB2,andto communicateinformationto eachotherabout thethread.TheDB2connection controlblockcontrols thethread withinDB2.TheCICSconnectioncontrolblock, called theCSUB,actsasa pointerto theDB2connectioncontrolblock,and containstheinformationCICSrequirestocall theDB2 connectioncontrolblock whenthethreadisneeded.DB2callstheseconnectioncontrolblocks “agent structures”.

Thenature ofthethreadTCBs,andthewayinwhichtheyarelinkedtotheDB2 connection controlblock(andthereforeto thethread),differs dependingonthe version ofDB2to whichCICSisconnected.

While CICSisconnecting toa DB2subsystem,it checkstheDB2releaselevelof thesubsystem.IfCICSisconnectingto DB2Version6orlater, theCICSDB2 task-related userexit(themodulethatinvokesDB2foreachtask) isautomatically enabled asopenAPI,soitcan usetheopen transactionenvironment(OTE).If CICSisconnectingto DB2Version5orearlier,thetask-relateduserexit isnot enabled asopenAPI,anddoes notusetheopen transactionenvironment.

Thread

TCBs

in

a

non-open

transaction

environment

When CICSisconnectedto DB2Version5orearlier,andsoisnotusingtheopen transaction environment,thethreadTCBsaresubtaskscreatedbytheCICSDB2 attachmentfacilityto runeach threadthatisrequestedbytransactionsorDB2 commands. TheCICSDB2task-relateduserexit itselfremains ontheCICSmain TCB, theQRTCB.

Oncecreated,thesubtaskthreadTCBsarepermanentlyassociatedwitha particularCSUBandDB2connectioncontrolblock.Whentheprocessfor whicha subtaskthreadTCBwascreatediscomplete,thesubtaskthreadTCB,CSUB,DB2 connection controlblockandthreadarereleased,andthewholeassemblycanbe reusedbyanotherCICStransaction toaccessDB2resources.Sotoreuse an existingthread,theCICSDB2attachmentfacilitymustalso reusethesubtask thread TCBassociatedwithit.

If thethreadisterminatedbefore itisreused,thesubtaskthread TCBandits associatedCSUBandDB2connectioncontrolblockremainavailableinthesystem. Like thethreadsthemselves,it takesprocessorresource tocreatethese,sothe CICSDB2attachmentfacilityreusesthem.If athreadisrequestedandnoexisting threadsareavailable,theCICSDB2attachmentfacilitylooksfor anunusedsubtask thread TCB,CSUBandDB2connection controlblock,andreusesthem toruna new threadintoDB2.

Figure2onpage5 summarizeshow threadTCBsoperateinanon-open transaction environment.

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In Figure2, situation1showsCICSusingathread toaccessDB2.OntheCICS main TCB,thelanguageinterfacethatislink-editedwiththeapplicationprogram callstheResourceManagerInterface(RMI),whichinvokestheCICSDB2 attachmentfacility’s task-relateduserexit.TheCICSDB2task-relateduserexit, operating ontheCICSmainTCB,usesanassembly consistingof asubtaskTCB,a CSUB,andaDB2connection controlblocktorunathreadinto DB2.Theplan associatedwiththethread isheldinDB2.

Situation 2showsa threadthatisnotcurrentlyinuse,butisprotected.The subtaskTCB,CSUBandDB2connection controlblockarestillassembledtogether, andthethread runsintoDB2.Thethreadisavailableforreuse.

Plan thread thread

DB2

CICS

Plan Subtask TCB DB2 connection control block CSUB

CICS main TCB

Application program Language Interface (stub) Resource Manager Interface (RMI) CICS DB2 TRUE 1 Subtask TCB DB2 connection control block CSUB 2 Subtask TCB DB2 connection control block CSUB 3

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Situation 3shows anassemblythatisleftafterathread wasterminated.The assembly, consistingof thesubtaskTCB,CSUBandDB2connection controlblock, isavailablefor reuse.It needsa newthread.

Thread

TCBs

in

the

open

transaction

environment

When CICSisconnectedto DB2Version6orlater, itisusingtheopen transaction environment.(Thissituationthereforeappliesto userswithDB2Version7orlater andJDBC2.0.)In thisenvironment,theCICSDB2attachmentfacilityusesopen TCBs (L8mode) asthethread TCBs,ratherthanusingspeciallycreatedsubtask TCBs.OpenTCBs performothertasksbesidesaccessingDB2resources.In the open transactionenvironment,theCICSDB2task-relateduserexit runsonanopen TCBratherthan ontheCICSmainTCB.Iftheapplicationprogramthatmade the DB2 requestisthreadsafe,it canalsorunontheopenTCB.(See“EnablingCICS DB2 applicationstoexploittheopentransaction environment(OTE)through

threadsafeprogramming”onpage106for moreinformationonapplicationprograms intheopentransactionenvironment.)

OpenTCBsarenotpermanentlyassociatedwithaCSUBandDB2connection controlblock.TheCICSDB2attachmentfacilitycanassociate themwithanyCSUB andDB2 connectioncontrolblockthatareavailable,andthereforewithanythread thatisavailable.WhentheopenTCBnolongerneedstheconnectionto DB2,it dissociatesfrom, orreleases,thethread,CSUBandDB2 connectioncontrolblock. Thethread,CSUBandDB2connection controlblockcanthenbeused bya differentopenTCBfor thetasksit wishestoperforminDB2.

If thethreadisterminatedbefore itisreused,theCSUBandDB2connection controlblockremainavailableinthesystem.Ifnoexistingthreadsareavailable, andanopenTCBneedsaconnectionto DB2,theCICSDB2attachmentfacility can associatetheunusedCSUBandDB2connection controlblockwiththeopen TCB, andreuse themto runa newthreadinto DB2.

Figure3onpage7 summarizeshow threadTCBsoperateintheopen transaction environment.

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In Figure3, situation1showsCICSusingathread toaccessDB2intheopen transaction environment.TheCICSDB2task-related userexithasbeeninvokedby theResourceManagerInterface (RMI),anditisoperating onanopenTCB.The CICSDB2attachmentfacilityhasassociateda CSUBanda DB2connectioncontrol blockwiththeopenTCB.TheDB2connection controlblockhasathreadinto DB2. Theplanassociatedwiththethread isheldinDB2.

Situation 2showsa threadthatisnotcurrentlyinuse,butisprotected.The CSUBandDB2connectioncontrolblockarestilllinked toeachotherandhave a thread,butnoopenTCBisattached tothem.Thethreadisavailablefor reuse. Situation 3showsanassemblythatisleftafterathread wasterminated.The CSUBandDB2connectioncontrolblockareavailableforreuse.Theyneedanew thread.

Situation 4showsopenTCBs thatareavailablefor reuse.TheCICSDB2 attachmentfacilitycanusetheseopenTCBsandassociateCSUBandDB2 connection controlblockassemblieswiththemto runthreadsintoDB2.

BothtypesofTCBthattheCICSDB2attachmentfacilityusestorunthethreads, theopenTCBs andthesubtaskTCBs,arereferredto inthis documentationas “thread TCBs”.In manysituations, thedifferentnature ofthetwotypesofthread TCBdoes notleadtoanydifferencesintheoperationof theCICSDB2connection.

Plan thread thread

DB2

CICS

1 DB2 connection control block CSUB 2 DB2 connection control block CSUB

Open

TCB

Open

TCB

4 3 DB2 connection control block CSUB

Open TCB

CICS DB2 TRUE Plan

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Where thedifferenttypesofthreadTCBdocausetheCICSDB2 connectionto behave differently,a distinctionismadebetweenthetwotypes.Formoretechnical informationonthreadTCBs,see“ThreadTCBs(task controlblocks)”onpage177.

Overview:

How

you

can

define

the

CICS

DB2

connection

You useresourcedefinitiononline(RDO)todefinetheCICSDB2connection.If you aremigratingfromanearlierreleaseofCICSandhavenotused RDObefore,read “MigratingfromaCICSreleasethatusedRCTdefinitionsfor CICSDB2 resources” onpage17.Ifyour CICSsystem isconnected toDB2Version6or later,the MAXOPENTCBSsystem initializationparameteralso influencestheCICSDB2 connection —formoreinformation,see “TheMAXOPENTCBSsysteminitialization parameter andTCBLIMIT”onpage52.

As wehavereadin“Overview:HowCICSconnectsto DB2”onpage 1,theCICS DB2 connectionconsistsofanoverallconnectionbetweenCICSandDB2,and individual connectionsknownasthreads.Youcandefinetheattributesoftheoverall connection,andtheattributesof thedifferenttypesof thread.Ifyou havespecially defined entrythreadsforkeytransactions,youcantell theCICSDB2attachment facilitywhichCICStransactionscanusethosethreads. DefiningtheCICSDB2 connection involvesthreedifferentobjects:DB2CONN(theDB2connection definition),DB2ENTRY(theDB2entrydefinition),andDB2TRAN(theDB2 transaction definition).Thescopeof eachobjectisasfollows:

DB2CONN

DB2CONN isthemain definitionfor theCICSDB2 connection.Youneedto install aDB2CONNbefore youcanstarttheCICSDB2connection.Inthe DB2CONN definition,you:

v Definetheattributesof theoverallCICSDB2 connection,whichare:

– theDB2 subsystemthatCICSconnectsto,or thedata-sharinggroup of

DB2subsystemsfromwhichDB2picksanactivememberforCICSto connectto

– iftheconnectionto DB2fails,whetherCICSreconnectsautomaticallyor

not,and,ifyouareusingthegroup attachfacility,whetherCICS reconnectstothesameDB2subsystemor not

– ageneral-purposeauthorizationIDfortheCICSDB2attachmentfacilityto

signontoathread,if nootherauthorizationisneededforthethread – thelimitonthetotal numberof TCBsthatCICScanusetorunthreads

intoDB2atanyonetime

– howlongprotected threadsarekept beforetermination

– howerrormessagesarecommunicated toCICS,andwhattransactions

shoulddoif theirthreadfails

– wheremessages andstatisticsaresent

v Definetheattributesof commandthreads(thespecialthreadsusedbythe

DSNCtransactionfor issuingDB2 commands),whichare:

– thelimitonthenumberof commandthreadsthatCICScanuseat any

onetime

– whattype ofauthorizationIDDB2checkswhenacommandthreadis

requested(for example,theIDof theuser, theIDof thetransaction,the general-purposeCICSDB2attachmentfacilityID)

v Definetheattributesof poolthreads(thegeneral-purposethreadsusedwhen

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– whattypeof authorizationIDDB2checkswhenapool threadisrequested

(forexample,theIDof theuser,theIDofthetransaction, the general-purposeCICSDB2attachmentfacilityID)

– whatthepriorityofthethreadTCBs isrelative totheCICSmainTCB

– thelimitonthenumberof poolthreadsthatCICScan useatanyonetime

– ifatransaction cannotgeta poolthread,whether itshouldwaitforone,or

beabended

– whatapplicationplanordynamicplanexit isused forthepoolthreads

(see“Plans,packagesanddynamicplanexits”onpage13)

– atwhatpointduringatransaction’suseof thethread DB2accounting

recordsareproduced

– ifthereisadeadlock,whether changesmade bythetransactionusingthe

threadarerolledback

You canhaveonly oneDB2CONNdefinitioninstalledinaCICSsystem atone time, andalltheDB2ENTRYandDB2TRANdefinitionsthatyouinstallinthe system areassociatedwiththeDB2CONNdefinition.If youdiscarda

DB2CONN definition,alltheDB2ENTRYandDB2TRANdefinitions are

discardedaswell.YoucannotdiscardaDB2CONN definitionandinstall another onewhileCICSisconnectedtoDB2.

You canstarttheCICSDB2connection withonly aDB2CONNinstalled—you donotneedanyDB2ENTRYandDB2TRANdefinitions tomaketheconnection. If youdothis, therearenospecialthreadsforkeytransactions(entrythreads). Alltransactionsusegeneral-purposethreadsfromthepool, andthemost important transactionshave towaitjustaslongastheleastimportant transactionsto gettheirindividual connectionintoDB2.Toensurethatyour important transactionsareprioritized,createDB2ENTRYand,ifnecessary, DB2TRANdefinitions forthem.

DB2ENTRY

You cansetupmanyDB2ENTRYdefinitions todefinedifferenttypesof entry threads.Theentrythreadscanbeusedbythetransactionsthatyou specify,to gain priorityaccess(orspecializedaccess)toDB2resources.In effect,youare reservingacertainnumberofthreadsthatcanonly beused bythose

transactions.Youcanalso protecta numberof eachtype ofentrythread,which improvesperformancefor heavily-usedtransactions.In aDB2ENTRYdefinition, youcan specifyaparticulartransaction,or (byusingawildcard)a groupof transactions,thatareassociatedwiththeDB2ENTRYandcanusethetypeof entry threadthatitdefines. Whenthosetransactionsrequestathread,theCICS DB2attachmentfacilitygivesthemthattypeof entrythread,ifoneisavailable. If youwantothertransactionsto usethesametypeof entrythread,youcan createaDB2TRANdefinitionforthosetransactions,whichsimplytellsCICS thatthetransactionsareassociatedwithaparticularDB2ENTRY.

In eachDB2ENTRYdefinition,you: v

Specifyatransaction, or(byusinga wildcardinthename)a groupof

transactions,thatcanusethistypeof entrythread

v Definetheattributesof thistypeof entrythread,whichare:

– whattypeof authorizationIDDB2checkswhenthistype ofentrythread is

requested(for example,theIDoftheuser, theIDof thetransaction,the general-purposeCICSDB2attachmentfacilityID)

– whatthepriorityofthethreadTCBs isrelative totheCICSmainTCB

– thelimitonthenumberof thistypeof entrythreadthatCICScanuseat

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– thenumberof thistypeof entrythreadthatareprotectedfor aperiodof

timewhiletheyarenotbeingused

– ifatransaction associatedwiththeDB2ENTRYcannotgetthistypeof

entrythread,whether itshouldwaitforthis typeofentry thread,overflow tousea poolthread,or beabended

– whatapplicationplanordynamicplanexit isused forthis typeofentry

thread(see“Plans,packagesanddynamicplan exits”onpage13) – atwhatpointduringatransaction’suseof thethread DB2accounting

recordsareproduced

– ifthereisadeadlock,whether changesmade bythetransactionusingthe

threadarerolledback

You cannotdiscardaDB2ENTRYwhiletransactionsareusingthattype ofentry thread —youmustdisable itfirst,to quiesceactivityontheDB2ENTRY,and then discardit.If youdiscardaDB2ENTRY,theDB2TRANsassociatedwithit are“orphaned”,andthetransactionslistedinthem willusepool threads. DB2TRAN

You canuseDB2TRANdefinitionsto associateadditionaltransactionswitha particularDB2ENTRY—thetransactionswillthenuse thattypeofentry thread. OnlyoneDB2TRANdefinitioncanbeinstalledfor aspecifictransaction.In each DB2TRANdefinition,yousimply:

v Specifythenameof aDB2ENTRY

v Specifyatransaction, or(byusinga wildcardinthename)a groupof

transactions,thatareassociatedwiththeparticularDB2ENTRYandcanuse thistypeof entrythread

Whenthosetransactionsrequestathread,theCICSDB2attachmentfacility seesthattheyareassociatedwiththeparticularDB2ENTRY,andtreatsthem like thetransactionortransactionsnamedontheDB2ENTRYdefinitionitself. You candefineandinstallDB2CONN,DB2ENTRYandDB2TRANobjects using RDO. Theobjects canalsobedefinedinbatchusingDFHCSDUP.CICSplex SM usesEXECCICSCREATEto installtheseobjects.Fordetailed informationabout how todefineeach oftheseobjects,seetheCICSResourceDefinitionGuide.

Overview:

Enabling

CICS

application

programs

to

access

DB2

ACICSapplicationprogramthataccessesDB2mustbepreparedinthesameway asa normalCICSapplicationprogram,andalso gothroughDB2’sbindprocess. Thebind processisaDB2processthatproducesanapplicationplan(often just called a“plan”).Eachplan containstheboundformofalltheSQLstatementsfrom theapplicationprogramsthatuseit,anditallowsthoseapplicationprogramsto accessDB2dataat executiontime.

TheplansareheldwithinDB2,andeach threadintoDB2relatesto aplan.The plan thateachtypeof threadusesisnamedontheDB2CONNdefinition(forpool threads)or thethread’s DB2ENTRYdefinition(forentry threads).Theplanfor a particulartypeof threadmust containtheboundformof theSQLstatementsfrom alltheapplicationprogramsthatusethattypeof threadto accessDB2.Youcan either nametheplanexplicitly,orname adynamicplanexit,a routinethat

determineswhich plantouse forthetransactionthathasrequestedathreadof that type.

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v “Thebindprocess”onpage12

v “Plans,packagesanddynamicplanexits”onpage13

Preparing

a

CICS

application

program

that

accesses

DB2

Figure4onpage12showsthestepsinpreparing aCICSapplicationprogramto accessDB2.

Thefirststep isto puttheprogramthroughtheDB2precompiler.TheDB2 precompiler buildsadatabaserequestmodel(DBRM)thatcontainsinformation about eachof theprogram’sSQLstatements.

Thesecond, thirdandfourthstepsarethenormalprocessfor preparinganyCICS applicationprogram,whetherornotit accessesDB2.Thesecondstepistoputthe programthroughtheCICScommandlanguagetranslator.Thethirdstepisto compileorassembletheprogram.Thefourth stepistolink-edittheprogramwith thenecessaryinterfaces(includingtheCICSDB2languageinterface module DSNCLI).TheendproductofSteps 2,3and4 isanapplicationload modulethat enables theprogramto run.Formoreinformationonthesesteps,see“CICSDB2 programpreparationsteps”onpage134.

An extrastepisrequiredtoenabletheprogramtousetheinformationintheDBRM thatwascreatedinStep1.This fifthstepisthebindprocess.Thebindprocess requiresDB2, anditusestheDBRMtoproduceanapplicationplan thatenables theprogramtoaccessDB2data.See“Thebindprocess”onpage12foran explanationofthebindprocess.

If youareusingoneof theLanguageEnvironment®-conformingcompilersfor COBOLandPL/I,youcancombinesomeof thesestepsintoa singletask,because thesecompilershaveintegratedtheCICScommandlanguagetranslator,and (dependingonyourversionof DB2)anSQLstatementcoprocessor.See“CICS DB2 programpreparationsteps”onpage 134formoreinformation.

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The

bind

process

Before anyCICSapplicationthataccessesDB2canrun,it needsto gothroughthe bind process.For thebindprocess,yourequire:

v DB2

v TheDBRM(databaserequestmodule)produced bytheDB2precompilerfor

eachprogramintheapplication.

TheDBRMcontainstheSQLstatementsthattheDB2precompilerhasextracted fromtheapplicationprogram.Inthebindprocess,theSQLstatementsintheDBRM areputintoanoperational(“bound”)form,bybeingtranslatedintothecontrol structuresthatDB2useswhenitrunsSQLstatements. Theresultingmaterialcan bemade intoapackage,oritcan beplacedstraightintoanapplicationplan(see “Plans,packagesanddynamicplanexits”onpage 13).Thewholeprocessiscalled “binding” theDBRM. Formoreinformationonbinding,seetheDB2Universal Database forOS/390andz/OSApplication ProgrammingandSQLGuide.See “Bindoptions andconsiderationsforprograms” onpage 138formoredetailon options youshouldchooseduringthebind processintheCICSDB2environment..

USER JCL AND SUBMIT TO BATCH OR

DB2I

(1) DB2 PRECOMPILER DBRM

(2) CICS COMMAND LANGUAGE TRANSLATOR

(3) COMPILE OR ASSEMBLE PROGRAM

(4) LINK EDIT WITH INTERFACES (5) BIND

APPLICATION LOAD MODULE PLAN

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Plans,

packages

and

dynamic

plan

exits

An applicationplan allowsapplicationprogramstoaccessDB2dataatexecution time. Itcontainsthebound(operational)formof theSQLstatementsfromthe DBRMsthatwerebuilt fromtheapplicationprograms.It alsorelatesthewhole applicationprocessto thelocalinstanceof DB2whereit willbeused.

TheoperationalSQLstatementsfromaDBRMcanbeplacedstraightintotheplan, inwhichcasewesaythattheDBRMisboundinto aplan.Alternatively,youcan bind aDBRMintoapackage(usingtheBINDPACKAGE command),which containstheoperationalSQLstatements froma singleDBRM.Youcangroup relatedpackagesintocollections.Youcanthen includethepackagename or collection nameinalistof packages,andbindthelistof packagesintotheplan.A single plancancontainbotha packagelist, andDBRMsbounddirectlyintothe plan. YoucancreateaplanusingtheDBRMsfromasingleCICSapplication,or you canusetheDBRMsfrommorethanoneapplicationtocreateasingleplan. As wellasbeingcreated,applicationplansneed tobemaintained.IftheSQL statements changeinoneor moreoftheapplicationprograms usinga plan,you need torebuildtheDBRMsfor thechangedapplicationprograms.Ifyouboundthe oldversionsof thoseDBRMsdirectlyintoyourplan, youneedto identifyallthe DBRMsthatarebounddirectlyinto thatplan,forboth thechanged programsand any unchangedprograms,andbindthemallintotheplan again.While youare binding theDBRMsintotheplan,applicationscannotusetheplanto accessDB2. However, ifyouboundtheoldversionsof theDBRMsfor thechanged application programs intopackages,andthenincludedthenamesof thepackages(orofthe collectionscontainingthem) onthepackagelistintheplan, youdonotneed tobind any otherpackagesordirectly-boundDBRMsinto theplan again.Yousimply bind thenew versionsof theDBRMsfor thechanged applicationprogramsinto

packageswiththesamenamesastheoldversions.You donotneedto bindthe plan again—itlocatesthenewversionsof thepackages. Whileyouarechanging thepackages,applicationprogramscanstillusetheotherpackagesand

directly-boundDBRMsintheplan. See“Whatto bindafteraprogramchange”on page 137formoreinformationonmaintainingplans.

Each threadintoDB2relatesto aplan—see“Overview:Howthreadswork”onpage 2 formoreinformationabout threads.Theplan thateach typeof threadusesis namedontheDB2CONNdefinition(forpoolthreads)or thethread’s DB2ENTRY definition(for entrythreads).WhenCICSrequeststheuseof athreadfor an applicationtoaccessDB2,it tellsDB2thename oftheplanassociatedwiththat type ofthread,andDB2locatestheplan.Thedefinitionforeach typeofthread can either namea specificplan, orit cannameadynamicplanexit, aroutinethat determineswhich plantouse forthetransactionthathasrequestedthethread. If thedefinitionof thepoolthreador entrythreadnamesa specificplan, allthe transactionsthatusethattypeof threadmust usethatplan.Thetransactionsthat can useatypeof entrythreadarespecifiedintheDB2ENTRYandDB2TRAN definitions forthethread.IftheDB2ENTRYdefinitionforthethread namesa specificplan, theDBRMsfromalltheapplicationprogramsthatcouldrununderall thosetransactionIDs mustbeboundintothesameplan,orboundintopackages thatarethenlistedinthesameplan.If theDBRMsfromanyof theapplication programs thatrununderthosetransactionIDs arebounddirectlyintotheplan, and you changetheSQLstatementsinanyofthoseapplicationprograms, thewhole plan willbeinaccessiblewhileyoubindallthedirectly-boundDBRMsintotheplan again.Thismeansthatnotransactioncanusethattypeof entrythreadwhileyou aremaintainingtheplan. Poolthreadscouldbeusedbyanyof yourCICS

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applicationsthataccessDB2,soiftheDB2CONNdefinitionnamesa specificplan for thepoolthreads,theplanneedstobepreparedandmaintainedusingthe DBRMsfromallthoseapplications. Ifanyof theDBRMshavebeen bounddirectly into theplan, thewholeplanwillbeinaccessibleduringmaintenance,andno transaction willbeableto useapoolthread.

There aretwoways toavoidmakingtypesofthread unavailablewhileyouare maintainingplans.Thebest solutionistoavoidbindingDBRMsdirectlyinto plans, byusingpackagesinstead.If youbindeach separateDBRMasapackageand include theminpackagelistsinplans,theplansarestillaccessiblewhileyouare maintainingindividualpackages. Whileyouarecarryingoutmaintenanceworkona particularprogram,thepoolthreadsorentrythreadsrelatedtoplansinvolvingthat programarestillavailable, becausetheplansarestillaccessible.Thismeansthat you cansafelynameaspecificplan foreach thread.Ifyou wantto startusing packages, see“Usingpackages”onpage90andtheDB2Universal Databasefor OS/390andz/OSApplicationProgrammingandSQLGuidefor detailsof howto implementpackages.

An alternativesolution,developedbeforepackageswereavailableinDB2,isto use a dynamicplan exit.Usinga dynamicplan exitmeansthatyoudonothave to name aspecificplanfor eachtypeof thread,soeven whenaparticularplan is inaccessibleduringmaintenance,thethreadsarestillavailable.Toimplementthis solution,youcreatemanysmallplansfor yourCICSapplications, eachcontaining theDBRMsfromafewclosely-related programs.Then,insteadof specifyinga plan name inthePLANattributeof theDB2CONNorDB2ENTRYdefinitionfor eachtype of thread,youspecifyanexitprograminthePLANEXITNAMEattribute.Whenan applicationprogramissuesitsfirstSQLstatementandacertaintype ofthread is requested,theexitprogramthatyouhavespecifiedinthethreaddefinitionselects theplan tousefor thatapplicationprogram.Ifa particularplanisinaccessible duringmaintenance,theapplicationprogramsrequiring thatplancannotusea thread,butotherapplicationprograms canusethesametype ofthreadwiththeir own plans.However,notethatonce aparticularinstanceof atypeof threadhas been createdforanapplicationprogramtouse, thatthreadinstanceisassociated withtheplanthatthedynamicplanexitselected.Foranotherapplicationprogram to reusethethread,itmust usethesameplan. Ifthedynamicplan exitselectsa differentplan fortheapplicationprogram,it mustfindorcreateadifferentthread withthecorrectplan.Thisreducestheopportunitiesforthread reuse.See“Dynamic plan exits”onpage96formore informationondynamicplanexits.

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Chapter

2. Installation

and

migration

notes

for

CICS

DB2

This chapterprovidesinformationyoushouldknowwhenyouareplanningand carrying outinstallationormigrationproceduresintheCICSDB2environment. v “CICSstartupJCLrequirements forconnection toDB2”

v “Supportedreleasesof DB2”

v “Migratingto adifferentreleaseofDB2”

v “Migratingfroma CICSreleasethatused RCTdefinitions forCICSDB2

resources”onpage17

CICS

startup

JCL

requirements

for

connection

to

DB2

TheCICSDB2attachmentfacilityhastoloadtheDB2programrequesthandler, DSNAPRH.Todothis,theDB2library,db2hlq.SDSNLOAD,shouldbeplacedinthe MVS linklist,oraddedtotheSTEPLIBconcatenation ofyourCICSjob(where db2hlqisyourchosenhigh-levelqualifier forDB2libraries).

TousetheDB2JDBCdriver shippedwithDB2Versions7or 8,the db2hlq.SDSNLOD2libraryalsoneedsto beaddedtotheCICSSTEPLIB

concatenation.TheDB2JDBCdriversshipped withDB2Versions 5and6donot requirethislibrary.

TomodifyyourCICSstartupJCLyoushouldconcatenatethefollowing librarieson theSTEPLIBDDstatementasfollows:

v db2hlq.SDSNLOAD(aftertheCICSlibraries)

v db2hlq.SDSNLOD2(aftertheCICSlibraries)

There shouldbenoDB2librariesintheDFHRPLDDstatement.If DB2librariesare requiredintheDFHRPLconcatenationbyanapplication,or byanotherproduct, they shouldbeplacedaftertheCICSlibraries.

Supported

releases

of

DB2

CICSsupports thefollowing releasesof DB2:

v DB2UniversalDatabaseServerfor OS/390Version6

v DB2UniversalDatabaseServerfor OS/390andz/OSVersion7

v DB2UniversalDatabaseServerfor OS/390andz/OSVersion8

CICSprovidesaCICSDB2attachmentfacility(theCICSDB2adaptor)thatworks withallsupportedreleasesof DB2.TheCICSDB2attachmentfacilityisshippedon theCICSTransactionServerproducttape, andyou mustusethisversion ofthe attachmentfacilitytoconnect aCICSTransactionServerregiontoDB2.

TheCICSDB2attachmentfacilityhasbeensuppliedbyCICSsinceCICS/ESA® 4.1.AlwaysusethecorrectCICSDB2attachmentfacilityforthereleaseof CICS under whicharegionisrunning—theCICS4.1attachmentfacilityfor aCICS4.1 region,andsoon.

Migrating

to

a

different

release

of

DB2

When youareplanningmigrationto anewerDB2release,considerthefollowing information:

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To usethe DB2groupattachfacility withCICS,CICSmustbeconnectedto DB2Version7 orlater.You mustalsouse DB2Version7orlater“early” (ERLY) code,meaningthattheDB2Version7or laterversionof db2hlq.SDSNLINKmust bepresentintheMVS linklist (wheredb2hlqisyourchosenhigh-levelqualifier for DB2 libraries).Youmustalso applyAPARSPQ44614, PQ45691,andPQ45692. (An MVS IPLisrequiredfor theseDB2APARSto takeeffect.)

Withthegroupattachfacility,insteadof connectingtoa specificDB2subsystem, you canchoosetoconnect toanyonememberof adata-sharinggroupof DB2 subsystemswhich isactive onanMVSimage.Thisallowsyoutousea common DB2CONN definition,specifyinga groupID,acrossmultipleclonedAORs,andto reconnectrapidlyif theconnection toDB2fails.See“UsingtheDB2groupattach facility”onpage51formoreinformation.

For theCICSDB2attachmentfacility tousetheopentransactionenvironment (OTE),CICSmustbeconnectedtoDB2Version6 orlater.You mustalsouse DB2 Version6 orlater“early” (ERLY)code,meaningthattheDB2Version6or later version ofdb2hlq.SDSNLINKmust bepresentintheMVS linklist. Ifyouareusing DB2 Version6 earlycode,youmustapplyAPARSPQ43242andPQ50703.If you areusingDB2Version7early code,youmust applyAPARSPQ46501and PQ50703. (AnMVS IPLisrequiredfor theseDB2APARSto takeeffect.)

Theopen transactionenvironmentenablestheCICSDB2task-relateduserexit to execute onanopenTCB.OpenTCBs,unliketheQRTCBorsubtaskthreadTCBs, may beused forbothnon-CICSAPIrequests (includingrequeststo DB2)and threadsafeapplicationcode.Because threadsafeapplicationcodecanbeexecuted ontheopenTCB,athreadsafeCICSDB2applicationshouldnotneedto switch betweendifferentTCBsseveraltimesduringtheexecutionof aCICSDB2 application.Thissituationproducesa significantperformanceimprovement where anapplicationprogramissues multipleSQLcalls.See“Enabling CICSDB2 applicationsto exploittheopentransactionenvironment (OTE)throughthreadsafe programming” onpage106for moreinformationontheopen transaction

environment anditsperformancebenefits.

If youare migratingtoDB2Version6orlater,notethatwitheffectfromDB2 Version6, theCICS-DB2languageinterfacemodule, DSNCLI,isnolongershipped bytheDB2product.CICSshipsthelanguageinterface stubinboth the

SDFHLOAD andSDFHAUTHlibraries asaCICSnamedmodule, butalso with appropriatealiasesforcompatibility. InSDFHLOAD,thestub iscalled DFHD2LI, withaliasesofDSNCLI,DSNHLI,andDSNWLI.In SDFHAUTH,thestub iscalled DFHD2LIX,withaliasesDSNCLI,DSNHLI,andDSNWLI.Ensure thatthelibrary concatenation fortheDB2librarySDSNLOADandtheCICSlibrarySDFHLOAD are correctfor yoursite,becausebothlibrariescontaintheDSNHLIalias.

If youare migratingtoDB2Version6orlater,andusingtheopentransaction environment,ensurethatthelimitsetinyourMAXOPENTCBSsysteminitialization parameter isgreater thanthelimitsetintheTCBLIMITattributeof yourDB2CONN definition. Intheopentransactionenvironment,MAXOPENTCBSdefines thetotal numberof openTCBsallowedintheCICSsystem,andTCBLIMITdefinesthe numberof theseopenTCBs thatcanbeused toconnect toDB2.If your

MAXOPENTCBSlimitislowerthanyourTCBLIMIT,awarning messageisissued whenCICSconnectstoDB2, andyoumayfindthatyoudonothave enoughopen TCBs availabletoprocess yourDB2workload.Inaddition,whenrunningwith TransactionIsolationactiveandconnectedtoDB2Version6 orlater,set

MAXOPENTCBSto thevalueof maxtasks(MXT)or higher.This willminimisethe # # # # # # # # #

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possibilityofTCBstealingduetoaTCBbeingallocatedtothewrongsubspace.For more information,see“TheMAXOPENTCBSsystem initializationparameterand TCBLIMIT” onpage52.

Migrating

from

a

CICS

release

that

used

RCT

definitions

for

CICS

DB2

resources

In releasesof CICSearlierthanCICSTransactionServerfor OS/390,Version1 Release2, theconnectionbetweenCICSandDB2wasdefinedintheresource controltable (RCT).TheRCTdescribedtherelationshipbetweenCICStransactions andDB2resources(applicationplansandcommandprocessors)andwas

generated usingtheDSNCRCTmacroprovidedbytheCICSDB2 attachment facility.VersionsandreleasesofCICSfromCICSTransactionServerfor OS/390, Version1 Release3onwardsdonotsupportrunningtheCICSDB2attachment facilityusingthemacroDSNCRCT.

If youaremigratingfromaCICSreleasethatdefinedtheCICSDB2connection usingaresource controltable,younow needtodefineDB2resource definitions usingCICSresourcedefinitiononline(RDO).MacroRCTscan stillbeassembled for thepurposeofmigratingthemtotheDFHCSD fileonly.TheDSNCRCTmacrois shipped withCICSto allowmigrationof RCTtablesto theCSD.Itisnow wholly owned by,andincorporatedin,CICS.For moreinformationaboutDSNCRCT,see CICSResourceDefinition Guide.

When describingparametersof theCICSDB2connection,thenamesofthe parametersof theRDO objectsarenowused,nottheDSNCRCTmacroparameter names.TheCICSResourceDefinitionGuidedescribeswhichDSNCRCTmacro parameter appliestowhich RDOparameter,andwhich RDOparameterapplies to which DSNCRCTmacroparameter.

AllchangesmadetoDB2 resourcedefinitionsinstalleddirectlyfromtheCSD,or made byusingEXECCICSCREATEcommands, arecatalogedandrecoveredina CICSrestart.Also,theDB2objectsinstalledfromtheCSDremaininstalledafterthe CICSDB2attachmentfacilityisstopped.

This topicprovidesinformationtoassist youwiththemigrationprocess,asfollows: v “Ifyouhave notused CICSresourcedefinitiononline(RDO)before”

v “EffectofmigrationtoRDO onCICSDB2attachmentfacilityoperations”onpage

18

v “EffectofmigrationtoRDO onapplicationprograms”onpage21

v “EffectofmigrationtoRDO ontheINITPARMsystem initializationparameter”on

page21

v “EffectofmigrationtoRDO ondefaults forresourcedefinitionparameters”on

page21

v “Migratingto RDOfor DB2resourcedefinition”onpage 21

If

you

have

not

used

CICS

resource

definition

online

(RDO)

before

Using onlineCICSDB2resource definitionmeansthatyoudonothaveto shut downtheinterfacebetweenCICSandDB2whenadding, deleting,orchanging CICSDB2resourcedefinitions.Thebenefits ofusingonlinedefinitionforDB2 resourcesarediscussedinthefollowingsections:

v Function

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v Performance

Function

Thefunction oftheCICSDB2attachmentfacilityisenhancedbyusingonline resource definitioninthefollowingways:

v Existingmacro-definedRCTload modulescanbeeasilymigratedto theCICS

systemdefinitionfile(CSD)usinganRCTmigrationutility.

v TheCICSDB2 attachmentfacilityisfullyintegratedintoCICSproviding

enhancedfirstfailuredata capture,enhancedmessages withNLSsupport,more tracingincludingexceptiontracing,andsystemdump supportwithformatting integratedinto theCICSIPCSverbexit.

v Itenables managementoftheCICSDB2interfacebyCICSplexSM,including

singlesystemimageandsinglepoint ofdefinitionacrossaCICSplex.

v TheCICSDB2 definitionsbecomeaCICS-managed resourcewhichprovidesa

consistentenduserinterface:

– CEDAandDFHCSDUPfor definingandinstallingentries

– EXECCICSCREATEforinstallingentries

– CEMT/EXECCICSINQUIRE,CEMT/EXEC CICSSET,andCEMT/EXEC

CICSDISCARD formanipulatinginstalledentries.

Enhancementsmadeto theCICSDB2attachmentfacilitybeforeCICS TransactionServerforOS/390,Version1Release3included:

– ImprovedCICSDB2statisticsintegratedwithCICS

– ImprovedattachmentfacilityshutdowncoordinatedwithCICSshutdown

– ImprovedTCBmanagement

– Improvedthreadmanagement anddisplays

– Anewaccounting option

System

availability

Online CICSDB2 resourcedefinitionallowsyouto add,deleteorchangedefinitions without theneedtoshut downtheinterface betweenCICSandDB2.Youare thereforeprovided withcontinuous availability.

Performance

Online CICSDB2 resourcedefinitionprovidesbenefits toperformanceasfollows: v CICSDB2controlblocksaremovedabovethe16MBlineprovidingvirtual

storageconstraintrelief(VSCR).

v OnlineCICSDB2resourcedefinitionprovidestheability tospecifygeneric

transactionnames,usingwildcardsymbols,whichcanreducethenumberof definitionsrequiredinCICS.

Effect

of

migration

to

RDO

on

CICS

DB2

attachment

facility

operations

Changesto theCICSDB2attachmentfacilityaffecttheoperation ofthefacilityin thefollowingways:

Attachment startupandshutdown

You canusetheDSNCSTRTcommandto starttheCICSDB2attachment facility.

Thesyntaxof theDSNCSTRTcommandisDSNCSTRTyyyy.Anyvalue specifiedaftertheSTRTistreatedasaDB2ID.ThisoverridesanyDB2IDor DB2GROUPIDspecifiedintheDB2CONNdefinition.Ifnovalueisspecified, the valuefromtheinstalledDB2CONNisused.If youwantto usegroupattach,do notspecifyavalueontheDSNC STRTcommand.

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CICSobtainstheIDof theDB2subsystemtowhich itconnectsfromoneofthe following sources,intheorderof priorityshown:

1. AsubsystemIDinaDSNCSTRTcommand,ifspecified.

2. ADB2ID intheinstalledDB2CONNresourcedefinition,if notblank.

3. ADB2GROUPIDintheinstalledDB2CONNforgroup attach,if specified.

4. AsubsystemIDspecifiedontheINITPARM systeminitialization parameter,

whentheDB2IDandDB2GROUPIDintheinstalledDB2CONNresource definitionareblank(orhavesubsequentlybeen settoblanks). Onany startup,INITPARM isalwaysused ifthelastinstalledDB2CONNcontained a blankDB2IDanda blankDB2GROUPID, eveniftheDB2IDor

DB2GROUPIDwere subsequentlychangedusingaSETcommand. 5. AdefaultsubsystemIDofDSN.

You canusetheDSNCSTOP<QUIESCE|FORCE>commandtostop theCICS DB2attachmentfacility.TheQUIESCEoptionnowwaitsfor allactive

transactionsto complete,thatis,new UOWscanstartandacquirethreads.In releasesofCICSearlierthanCICSTransactionServerforOS/390,Version1 Release2, aquiescewouldonlywaitforactivetransactionstoreleasetheir thread,which,typically, wasat theendof aunitof work(UOW).

Duringshutdownof theCICSDB2 attachmentfacilityinitiatedbyDSNCSTOP, theterminalremains lockeduntilthestopiscomplete,whenmessage

DFHDB2025isissued.

As analternativeto theDSNCcommand,youcanstartandstop theCICSDB2 attachmentfacilityusingtheEXECCICSSETDB2CONN

CONNECTED|NOTCONNECTEDcommands.You canalsostop theCICSDB2 attachmentfacilitybystartingtheCICS-suppliedtransactionsCDBQandCDBF fromanapplicationprogram,usinganEXECCICSSTARTcommand.CDBQ causes aquiescecloseandCDBFcauses aforceclose.

CICSDB2attachmentfacilitycommandchanges

Thepoolsection oftheDB2CONNresourcedefinitiondoes nothaveaTXID parameter associatedwithit.Tomodifythenumberof threadsallowedonthe pool, usereservedname CEPLontheDSNC MODIFYTRANScommand.For example,issuethefollowingcommand(wheren isthenew numberof threads).

DSNC MODIFY TRANS CEPL n

TheDSNC DISPTRANttttcommandnowdisplaysallthreadsrunningfor a particulartransid,insteadof allthetransactionsassociatedwithanRCTentry. In earlierreleases,CICSusesthettttoperandtolocateanRCTentryandthen displaysallthethreadsfor thatentry.

Whenyou usetheDSNC DISPSTATcommand,CICSdisplaysstatisticsfor DSNC commandsonalinebeginning’*COMMAND’.Poolthreadstatistics are displayed ona linebeginning’*POOL’.

WhenmodifyinganRCTentryusingtheDSNC MODIFYTRANSttttcommand, specifyttttexactlyasitwasdefinedintheRCT. Ifyoudefineda genericTXID, youmust refertothegenericnamewhenmodifyingit witha DSNCcommand. For example,ifyouhave transactionscalledTABandTAC,butthey aredefined genericallyasTA*,youcan modifytheseonaDSNC commandonly bytheir genericname:

CICS Transaction Server for z/os. CICS DB2 Guide. Version 3 Release 1 SC

CICS

Transaction

Server

for

z/OS

CICS

DB2

Guide

Version

3

Release

1

CICS

Transaction

Server

for

z/OS

CICS

DB2

Guide

Version

3

Release

1

Contents

Preface

What

this

book

is

about

What

you

need

to

know

to

understand

this

book

Notes

on

terminology

Summary

of

changes

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

3

Release

1

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

2

Release

3

Changes

for

CICS

Transaction

Server

for

z/OS,

Version

2

Release

2