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IBM SC34-7012-01 manual Part 1. CICS recovery and restart concepts

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Part 1. CICS recovery and restart concepts

It is very important that a transaction processing system such as CICS can restart and recover following a failure. This section describes some of the basic concepts of the recovery and restart facilities provided by CICS.

© Copyright IBM Corp. 1982, 2010

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IBM SC34-7012-01 manual Part 1. CICS recovery and restart concepts

Contents

CICS Transaction Server for z/OS Recovery and Restart GuideVersion 4 Release SC34-7012-01Page CICS Transaction Server for z/OS Recovery and Restart GuideVersion 4 Release SC34-7012-01Copyright IBM Corporation 1982 Part 1. CICS recovery and restart concepts ContentsPart 2. Recovery and restart processes Chapter 2. Resource recovery in CICSChapter 9. Communication error Part 3. Implementing recovery andrecovery Chapter 8. Unit of work recovery andChapter 16. Moving recoverable data Chapter 13. Programming for recoveryChapter 17. Forward recovery Chapter 18. Backup-while-open BWOAccessibility Chapter 19. Disaster recoveryPart 4. Appendixes NoticesPreface How to use this bookWhat this book is about Who should read this bookviii CICS TS for z/OS 4.1 Recovery and Restart Guide Changes in CICS Transaction Server for z/OS, Version 4 Release x CICS TS for z/OS 4.1 Recovery and Restart Guide Part 1. CICS recovery and restart concepts 2 CICS TS for z/OS 4.1 Recovery and Restart Guide Maintaining the integrity of data Chapter 1. Recovery and restart facilitiesLogging changes The role of CICS Minimizing the effect of failures4 CICS TS for z/OS 4.1 Recovery and Restart Guide CICS backward recovery backout Recoverable resourcesEmergency restart backout Dynamic transaction backoutForward recovery of CICS data sets CICS forward recoveryCICS recovery processing following a communication failure Failures that require CICS recovery processingForward recovery for non-VSAM resources XCF/MRO partner failures CICS recovery processing following a system failure CICS recovery processing following a transaction failure10 CICS TS for z/OS 4.1 Recovery and Restart Guide v Back out recoverable resources 12 CICS TS for z/OS 4.1 Recovery and Restart Guide Units of work Chapter 2. Resource recovery in CICSShunted units of work Active and retained states for locks LocksEXEC CICS CREATE TERMINAL EXEC CICS CREATE CONNECTION COMPLETE Synchronization pointsEXEC CICS DISCARD CONNECTION EXEC CICS DISCARD TERMINAL EXEC CICS CREATE TERMINALEXEC CICS CREATE CONNECTION COMPLETE EXEC CICS DISCARD CONNECTION Examples of synchronization pointsEXEC CICS DISCARD TERMINAL CICS recovery manager Recovery FC/RLSv Coordinating recoverable conversations to remote nodes Figure 3. CICS recovery manager and resources it works withCoordinating updates to local resources Managing indoubt units of work Coordinating updates in distributed units of workCICS system log Resynchronization after system or connection failureInformation recorded on the system log System activity keypoints Forward recovery logsUser journals and automatic journaling Input or output messages from terminals accessed through VTAM 24 CICS TS for z/OS 4.1 Recovery and Restart Guide Normal shutdown processing Chapter 3. Shutdown and restart recoveryFirst quiesce stage Third quiesce stage Second quiesce stageShunted units of work at shutdown Warm keypointsImmediate shutdown processing PERFORM SHUTDOWN IMMEDIATE Flushing journal buffersPERFORM IMMEDIATE not recommended Shutdown requested by the operating system The shutdown assist transaction Uncontrolled termination30 CICS TS for z/OS 4.1 Recovery and Restart Guide Global catalog Cataloging CICS resourcesLocal catalog Shutdown initiated by CICS log manager Effect of problems with the system logDFHRM0402 How the state of the CICS region is reconstructedDFHRM0403 and DFHRM0404 DFHRM0405Warm restart Overriding the type of start indicatorEmergency restart About this taskCold start Recovery of data during an emergency restartAn initial start of CICS Dynamic RLS restart Running with persistent sessions support Recovery with VTAM persistent sessionsSNPS, single-node persistent sessions MNPS, multinode persistent sessionsSituations in which sessions are not reestablished Situations in which VTAM does not retain sessions Running without persistent sessions supportSET VTAM FORCECLOSE SET VTAM IMMCLOSE SET VTAM CLOSED regions that do have persistent sessions support 42 CICS TS for z/OS 4.1 Recovery and Restart Guide Part 2. Recovery and restart processes 44 CICS TS for z/OS 4.1 Recovery and Restart Guide Starting CICS with the START=COLD parameter Chapter 4. CICS cold startAbout this task VSAM FilesTransient data Temporary storageTemporary storage data sharing server Data tablesTransactions Resource definitions dynamically installedJournal names and journal models LIBRARY resourcesSingle resource install Committing and cataloging resources installed from the CSDMonitoring and statistics Terminal control resourcesDistributed transaction resources Installable set installDump table Starting CICS with the START=INITIAL parameterinformation saved in the system log from a previous run. The primary and secondary system log streams are purged and CICS begins writing a new system log 52 CICS TS for z/OS 4.1 Recovery and Restart Guide Rebuilding the CICS state after a normal shutdown Chapter 5. CICS warm restartData set name blocks Reconnecting to SMSVSAM for RLS accessRecreating non-RLS retained locks FilesTDINTRA=EMPTY TDINTRA=NOEMPTY the defaultTrigger levels for TERMINAL and SYSTEM only Temporary storageTransactions No autoinstall for programsLIBRARY resources ProgramsStart requests Autoinstall for programsMonitoring and statistics TCAM and sequential BSAM devices CSD-defined resource definitionsJournal names and journal models Terminal control resourcesv Different TCT from last run. CICS installs the TCT only, and does not apply the warm keypoint information, effectively making this a cold start for these devices URIMAP definitions and virtual hostsDistributed transaction resources 60 CICS TS for z/OS 4.1 Recovery and Restart Guide Recovering information from the system log Recovering after a CICS failureChapter 6. CICS emergency restart Driving backout processing for in-flight units of workOther backout processing Effect of delayed recovery on PLTPI processingRebuilding the CICS state after an abnormal termination 62 CICS TS for z/OS 4.1 Recovery and Restart GuideRLS restart processing and orphan locks Reconnecting to SMSVSAM for RLS accessRecreating non-RLS retained locks Temporary storageStart requests 64 CICS TS for z/OS 4.1 Recovery and Restart GuideTerminal control resources CSD-defined resource definitionsDistributed transaction resources is successful, but CICS abnormally terminates before the catalog can be updated, CICS recovers the information from the forward recovery records on the system logTCAM and sequential BSAM devices 66 CICS TS for z/OS 4.1 Recovery and Restart Guide CICS ARM processing Chapter 7. Automatic restart managementRestrictions Waiting for predecessor subsystems Registering with ARMDe-registering from ARM Before you beginARM couple data sets Failing to registerCICS restart JCL and parameters Chapter 7. Automatic restart managementWorkload policies Connecting to VTAMCICS START options Messages associated with automatic restart The COVR transactionAutomatic restart of CICS data-sharing servers Server ARM processingCANCEL RESTART=NOYES Server commands for ARM supportWaiting on events during initialization Server initialization parameters for ARM supportUnit of work recovery Chapter 8. Unit of work recovery and abend processingIn-flight-failed Commit-failedBackout-failed Transaction backoutIndoubt-failed BDAM files and VSAM ESDS files FilesCICS data tables Intrapartition transient data START with recoverable data no PROTECTAuxiliary temporary storage START requestsSTART with nonrecoverable data no PROTECT START with recoverable data PROTECTSTART with nonrecoverable data PROTECT Restart of started transactionsEXEC CICS CANCEL requests Basic mapping support BMS messagesAuxiliary temporary storage Backout-failed recoveryTransient data I/O errorRetrying backout-failed units of work Disposition of data sets after backout failuresLogical delete not performed Open errorSMSVSAM server failure Duplicate key error DFSMSdss non-BWO backup in progressSMSVSAM server recycle during backout Coupling facility cache structure failureLock structure full error Commit-failed recoveryNone of the above Files Indoubt failure recoveryIntrapartition transient data Investigating an indoubt failureAuxiliary temporary storage The WAITSTATE of Shunted shows that this UOW has been suspended We can now see that Cache failure support Recovery from failures associated with the coupling facilityRebuilding the lock structure Lost locks recoveryNotifying CICS of SMSVSAM restart About this task90 CICS TS for z/OS 4.1 Recovery and Restart Guide Performing lost locks recovery for failed units of workConnection failure to a coupling facility cache structure MVS system recovery and sysplex recoveryConnection failure to a coupling facility lock structure Exit code Transaction abend processingTransaction restart Abnormal termination of a taskProcessing operating system abends and program checks Actions taken at transaction failurev If a match is not found, CICS is terminated 96 CICS TS for z/OS 4.1 Recovery and Restart Guide Terminal error processing Chapter 9. Communication error processingNode error program DFHZNEP Terminal error program DFHTEPIntersystem communication failures Part 3. Implementing recovery and restart 100 CICS TS for z/OS 4.1 Recovery and Restart Guide Questions relating to recovery requirements Chapter 10. Planning aspects of recoveryApplication design considerations Validate the recovery requirements statement End user’s standby procedures Designing the end user’s restart procedureCommunications between application and user About this taskSystem recovery table SRT System definitions for recovery-related functionsResource definitions for recovery SecurityTransient data queues Documentation and test plansTemporary storage table Program list table PLTv Forecast the exceptional conditions that can be expected Forward recovery logging recovery purposes onlyChapter 11. Defining system and general log streams System loggingDefining system log streams Defining log streams to MVSSystem log streams General log streamsWithout a JOURNALMODEL definition Specifying a JOURNALMODEL resource definitionWith a JOURNALMODEL definition Model log streams for CICS system logs Recovery considerations2-Way Sysplex Varying the model log stream name Activity keypointingAbout this task About this task Keeping system log data to a minimumMoving units of work to the secondary log Log-tail deletionAbout this task Avoiding retention periods on the system log Writing user-recovery dataRetrieving user records from the system log About this taskAbout this task Procedure Defining forward recovery log streamsLong-running transactions About this taskWhat to do next Model log streams for CICS general logsDefining the log of logs Merging data on shared general log streamsAbout this task Reading log streams offline Log of logs failureAbout this task About this taskEffect of daylight saving time changes Adjusting local timeTime stamping log and journal records About this taskOffline utility program, DFHJUP 122 CICS TS for z/OS 4.1 Recovery and Restart Guide Recovery for transactions Chapter 12. Defining recoverability for CICS-managed resourcesDefining transaction recovery attributes RESTARTNOYESSPURGENOYES Indoubt options for distributed transactionsTPURGENOYES ACTIONBACKOUTCOMMITFile-owning regions and RLS access Recovery for filesVSAM files Sharing data sets with batch jobsDefining files as recoverable resources Basic direct access method BDAMForward recovery Backward recoveryRECOVERYALL VSAM files accessed in non-RLS modeRECOVERYBACKOUTONLY BACKUPTYPEDYNAMICInquiring on recovery attributes VSAM files accessed in RLS modeLOGNONEUNDOALL NONEBDAM files File recovery attribute consistency checking non-RLSThe CSD data set Overriding open failures at the XFCNREC global user exitAbout this task CICS responses to file open requestsImplementing forward recovery with CICS VSAM Recovery MVS/ESA Implementing forward recovery with user-written utilitiesRecovery for intrapartition transient data Backward recoveryPhysical recovery Logical recoveryNo recovery Forward recoveryInput extrapartition data sets Recovery for extrapartition transient dataRecovery for temporary storage Using post-initialization PLTPI programsOutput extrapartition data sets Backward recoveryConfiguring CICS to support persistent messages Recovery for Web servicesForward recovery GROUPTSRECOV PREFIXDF LOCATIONAUXILIARY RECOVERYYESProcedure Defining local queues in a service providerResults What to do next ProcedurePersistent message processing Error processingFor example, your recovery transaction could 140 CICS TS for z/OS 4.1 Recovery and Restart Guide Designing applications for recovery Chapter 13. Programming for recoverySplitting the application into transactions About this task Procedure142 CICS TS for z/OS 4.1 Recovery and Restart Guide Example What to do next Relationships between processing unitsProgram design SAA-compatible applicationsDividing transactions into units of work ProcedureConversational processing Processing dialogs with usersPseudoconversational processing Mechanisms for passing data between transactions CICS recoverable resourcesMain storage areas Temporary storage auxiliary Designing to avoid transaction deadlocksTransient data queues User files and DL/I and DB2 databasesProcedure Implications of interval control START requestsImplications of automatic task initiation TD trigger level Using transient data queuesImplications of presenting large amounts of data to the user Terminal paging through BMSTransaction failures Managing transaction and system failuresAbout this task About this taskEXEC CICS SYNCPOINT ROLLBACK command HANDLE ABEND commandsDynamic transaction backout System failures Use of the program error program DFHPEPHandling abends and program level abend exits Transaction restart after DTBCommand Processing the IOERR conditionInformation provided PL/I programs and error handling START TRANSID commandsLocking enqueuing on resources in application programs Implicit locking for files Nonrecoverable filesAbout this task Recoverable files v READ for UPDATE v WRITE v DELETE Implicit enqueuing on recoverable temporary storage queues Implicit enqueuing on logically recoverable TD destinationsv WRITEQ TD v READQ TD v DELETEQ TD Explicit enqueuing by the application programmer Implicit enqueuing on DL/I databases with DBCTLDirect methods HDAM, HIDAM Sequential methods HSAM, HISAM, SHISAMdeadlock Possibility of transaction deadlockUser exits for transaction backout Where you can add your own codeAbout this task XRCINPT exit XRCINIT exitXFCBFAIL global user exit ProcedureXFCBOVER global user exit XFCLDEL global user exitXFCBOUT global user exit Coding transaction backout exitsThe CICS-supplied PEP Chapter 14. Using a program error program PEPProcedure About this taskYour own PEP Chapter 14. Using a program error program PEP Omitting the PEPAbout this task 166 CICS TS for z/OS 4.1 Recovery and Restart Guide Quiescing RLS data sets Chapter 15. Resolving retained locks on recoverable resourcesAbout this task About this taskIllustration of the quiesce flow across two CICS regions The RLS quiesce and unquiesce functionsChapter 15. Resolving retained locks on recoverable resources Other quiesce interface functions Non-BWO data set backup startBWO backup start Non-BWO data set backup endBWO backup end Forward recovery completeLost locks recovery complete Switching from RLS to non-RLS access modeException for read-only operations Quiesce coupling facility cache availableWhat can prevent a switch to non-RLS access mode? Investigating which retained locks are held and why Resolving retained locks before opening data sets in non-RLS modeProcedure About this taskINQUIRE UOWDSNFAIL INQUIRE DSNAMEAbout this task Resolving retained locks and preserving data integrity SHCDS LIST subcommandsAbout this task Procedure 176 CICS TS for z/OS 4.1 Recovery and Restart GuideAbout this task Choosing data availability over data integrityThe batch-enabling sample programs CEMT command examplesDFH0BAT1 DFH0BAT2STATUS RESULTS - OVERTYPE TO MODIFY SET DSNAME’RLS.ACCOUNTS.ESDS.DBASE1’ RETRYDsnRLS.ACCOUNTS.ESDS.DBASE1 NORMALThe DENYNONRLSUPDATE subcommand The PERMITNONRLSUPDATE subcommandA special case lost locks Overriding retained locksPost-batch processing Coupling facility data table retained locks Procedure for moving a data set with retained locks Chapter 16. Moving recoverable data sets that have retained locksUsing the REPRO method About this taskSHCDS FRSETRR SHCDS FRRESETRRSHCDS FRUNBIND SHCDS FRBINDChapter 16. Moving recoverable data sets that have retained locks Using the EXPORT and IMPORT functionsAbout this task About this task Rebuilding alternate indexesForward recovery of data sets accessed in RLS mode Chapter 17. Forward recovery proceduresAbout this task 3. Issue FRSETRR Recovery of data set with volume still available4. Issue FRUNBIND 5. Restore the backup10. Issue the FRBIND subcommand Recovery of data set with loss of volume11. Issue the FRRESETRR subcommand 9. Alter the new data set nameVolume recovery procedure using CFVOL QUIESCE 1. VARY SMS,CFVOLvolser,QUIESCE Example of recovery using data set backup 5. We terminated the SMSVSAM servers using the MVS command INQUIRE UOWDSNFAIL DSNRLSADSW.VF01D.BANKACCT 194 CICS TS for z/OS 4.1 Recovery and Restart GuideThese commands are issued to each CICS AOR that requires access 196 CICS TS for z/OS 4.1 Recovery and Restart Guide Example of recovery using volume backupCatalog recovery Procedure for failed RLS mode forward recovery operation Forward recovery of data sets accessed in non-RLS mode3. Restore the backup 4. Run the forward recovery utility1. Tidy up any outstanding CICS recovery work, as follows 1 Force shunted indoubt units of work using SET DSNAME Procedure for failed non-RLS mode forward recovery operation 202 CICS TS for z/OS 4.1 Recovery and Restart Guide BWO and backups Chapter 18. Backup-while-open BWOBWO and concurrent copy Component name BWO requirementsFull DFSMS/MVS name Previous productWhich data sets are eligible for BWO Hardware requirementsVSAM control interval or control area split How you request BWO Specifying BWO using access method servicesResults TYPECICSAbout this task Specifying BWO on CICS file resource definitionsRemoving BWO attributes Systems administrationBatch jobs ProcedureBWO processing File opening First file opened in non-RLS mode against a clusterBack-level data sets Subsequent files opened when use count is zero Subsequent files opened when use count is not zeroRestriction for VSAM upgrade set File closing non-RLS modeShutdown and restart Data set backup and restoreControlled shutdown Immediate or uncontrolled shutdownInvalid state changes for BWO attributes VSAM access method servicesData set restore Forward recovery loggingData sets Non-SMS managed storageForward recovery Recovery point non-RLS modeAbout this task Recovering VSAM spheres with AIXsAn assembler program that calls DFSMS callable services DTTENTHS DATETIMERECOVPTP DATEPACKPRGCONT 220 CICS TS for z/OS 4.1 Recovery and Restart GuideBWOFLAGS12,ZEROES LOADEND PROG 222 CICS TS for z/OS 4.1 Recovery and Restart Guide Why have a disaster recovery plan? Chapter 19. Disaster recoveryDisaster recovery testing Tier 0 no off-site data Six tiers of solutions for off-site recoveryTier 1 - physical removal The drawbacks are Tier 3 - electronic vaulting Tier 2 - physical removal with hot siteTier Tier 0-3 solutions Tier 0 Tier 4 - active secondary site230 CICS TS for z/OS 4.1 Recovery and Restart Guide Figure 22. Disaster recovery tier 4 active secondary siteTier 6 - minimal to zero data loss Tier 5 - two-site, two-phase commitFigure 24 summarizes the tier 6 solution Tier 4 Tier 4-6 solutionsPeer-to-peer remote copy PPRC and extended remote copy XRC Disaster recovery and high availabilityPPRC or XRC? Use XRC for high volume transactionsUse PPRC for high value transactions Other benefits of PPRC and XRC Remote Recovery Data FacilityForward recovery 236 CICS TS for z/OS 4.1 Recovery and Restart GuideDisaster recovery personnel considerations Choosing between RRDF and 3990-6 solutionsAbout this task RRDFMVS system logger recovery support Disaster recovery facilitiesReturning to your primary site 238 CICS TS for z/OS 4.1 Recovery and Restart GuideRemote Recovery Data Facility support CICS VSAM Recovery QSAM copyRemote site recovery for RLS-mode data sets CICS VR shadowingFinal summary Copyright IBM Corp. 1982 Part 4. Appendixes242 CICS TS for z/OS 4.1 Recovery and Restart Guide Notices 244 CICS TS for z/OS 4.1 Recovery and Restart Guide TrademarksAdministration Access to CICSBibliography CICS books for CICS Transaction Server for z/OSCICSPlex SM books for CICS Transaction Server for z/OS Administration and ManagementOther CICS publications GeneralAccessibility 248 CICS TS for z/OS 4.1 Recovery and Restart Guide Index A files continued DL/I continuedlocking continued Page Recovery and Restart Guide Publication No. SC34-7012-01 Readers’ Comments - Wed Like to Hear from YouCICS Transaction Server for z/OS Version 4 Release SC34-7012-01 Readers’ Comments - Wed Like to Hear from YouSC34-7012-01 IBM United Kingdom LimitedPage SC34-7012-01