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Theinsandoutsofjournaling

--PartI

Whatjournalingisandhowitworks

Journaling,generallyspeaking,isaprocessofrecordingactivity.

Inaccounting,itistheprocessofrecordingfinancialactivity--moniesinandmoniesout.

OntheiSeries,journalingreferstotheprocessofrecordingobjectactivity.

JournalingontheiSeriestypicallyinvolvestherecordingoftheactivityrelatedtofiles,namely,physicalfiles.

Whenafileisbeingjournaled,activitysuchasfile-opens,file-closesanddataupdatesarerecorded.

Forexample,whenaprogramwritesoutanewrecordorupdatesanexistingone,

thesystemmakesanentryintheassociatedjournal.Theentrycontainssuchinformationasthejobnameandprogramnamethatmadethechange(s)tothefile,aswellasacopyoftherecordthatwaschanged.

(Note:Journalingcanbeconfiguredtorecordacopyoftherecordbeforeitischangedand/ortorecordacopyoftherecordafteritischanged.)

Howtosetupjournalinginthreeeasy

steps

1.

Createoneormorejournalreceivers.UsetheCreateJournalReceiver(CRTJRNRCV)commandtocreateajournalreceiver.

Thinkofthejournalasanotebookbinderandthejournalreceiverasthepages(i.e.,thenotebookpaperwhereinformationiswritten).

Thejournalreceiveriswherethejournalentriesareactuallyrecorded.

Thejournal"connects"thereceivertothefile.It'sagoodhabittonamethejournalreceiverthesameasthejournal,plusanumericsuffixsuchas0or1.(Seethenextsteponwhattonamethejournal.)Also,youshouldputjournalreceiversinthesamelibraryasthefile.(Thisisveryimportantinordertosimplifyrecoveryprocedures,whichwewilldiscussinPartIII.)Formaximumprotection,considerstoringthejournalreceiverinadifferentASPthanthefilesothattheirstoragewillnotbeonthesamediskunit.

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Steps2.

Createajournal.UsetheCreateJournal(CRTJRN)commandtocreateajournalandspecifythereceivercreatedinstep1.Althoughyoucanjournalmultiplefilestothesamejournal(and,insomecases,thatisactuallypreferable),youwillgenerallywanttohaveajournal"serving"asinglefile.

Agoodpracticeistonamethejournalthesameasthefileandputitinthesamelibraryasthefile,butstoreitinthesameASPasthejournalreceiver.

Steps3.

Startjournalingthefile.

ThisisdonebyusingtheStartJournalPhysicalFile(STRJRNPF)command.Thisishowyouassociateafiletoajournal.Oncetheassociationismade,thesystemwillrecordinthejournalreceiveracopyofanyrecordadded,updatedordeletedfromthefile.Otheractivity,suchaswhenthefileisopenedandclosed,canalsoberecordedinthejournalreceiverifyouchoosebyselectingtheappropriateoptionsontheSTRJRNPFcommand.

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Formoreinformationonthejournalcommandsmentionedaboveandotherjournal-relatedcommands,pleaseseethesubsequentsection"Quickreferencetojournalingcommands.

"

Fourbasicjournalentrycategories

Themostcommonjournalentriesfallintofourbasiccategories.Eachcategoryisrepresentedbyaone-charactercode(showninparenthesisinthefollowinglist).Withineachcategoryareanumberofdifferentjournalentrytypes.

Eachjournalentrytypeisrepresentedbyatwo-characterentrycode(alsoshowninparenthesiswithinthecategorydescriptionsbelow).

1.Journalandjournalreceiveroperations(J).Theseincludesuchthingsasreferencestothepreviousreceiver(PR)orthenextreceiver(NR)inachain.Also,atIPL-time,anentryismade(e.g.,anINentryforIPLafternormalend)

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markingacriticalchronologicalboundaryinthefileactivity.

2.Fileoperations(F).Thiscategoryincludesfileopens(OP)andfilecloses(CL).

3.Recordoperations(R).Recordupdates(UP),deletes(DL),andnewrecordswritten(PTandPX)allfallintothiscategory.

4.Commitmentcontrol(C).Anythingrelatedtocommitmentcontrolfallsintothiscategory.Someexamplesarebegincommitmentcontrol(BC),startacommitcycle(SC),commitoperation(CM)androllbackoperation(RB).

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Thereareothercategoriesandentrytypesinadditiontothoselistedabove.However,thosearewhatyouwillcomeacrossmostoften.Foracompletelisting,seethedocumentationoronlinehelp.

Quickreferencetojournalingcommands

APYJRNCHG.Usesthejournalentriestoapplychangesthathaveoccurredsincea

databasefilewassavedorsomeotherspecifiedtime.

CHGJRN.Usethiscommandtochangetheattributesofajournalortoattachnewjournalreceiverstoajournal.

CMPJRNIMG.Thiscommandcomparesandliststhedifferencebetweenthebefore-imageandafter-imageofarecord,orbetweenthecurrentafter-imageofarecordandthepreviousafter-imageoftherecord.

CRTJRN.Usethiscommandtocreateajournal.

CRTJRNRCV.Usethiscommandtocreateajournalreceiver.

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DLTJRN.Usethiscommandtodeleteajournal.

DLTJRNRCV.Usethiscommandtodeleteajournalreceiver.

DSPJRN.Thiscommanddisplaysorprintsthejournalentriesthatareinthejournalreceiversassociatedwiththespecifiedjournal.Thiscommandhasoutfilesupportsoyoucanlistthejournalentriestoadatabaseoutputfileforfurtherprocessingoranalysis.

DSPJRNRCVA.Usethiscommandtodisplaytheattributesofajournalreceiver.

ENDJRNPF.Thiscommandendsjournalingforthespecifiedphysicalfile.

RCVJRNE.Thiscommandallowsaspecifieduserprogramtocontinuouslyreceivejournalentriesoneatatimeastheyarewrittentothejournal.Thebehaviorissimilartoanexitprogram.

RMVJRNCHG.Usethiscommandtoremovechangesthathaveoccurredtoadatabasefilefromaspecifiedpointintimetosomepreviouspointintime(allowedonlyifbefore-imageswererecordedduringthetime).

RTVJRNE.UsethiscommandtoretrieveajournalentryandplaceitinCLprogramvariables.

SNDJRNE.Usethiscommandtowriteuser-definedentriestoajournal(i.e.,journalreceiver).

STRJRNPF.Usethiscommandtostartjournalingforthephysicalfile.

WRKJRN.Thiscommanddisplaysamenufromwhichyoucanperformmanyjournal-relatedfunctions,suchassystem-assistedrecoveryofjournaledfiles.

WRKJRNA.Thiscommanddisplaystheattributesofajournalandtheassociatedreceivers.

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========================================================================================================

Theinsandoutsofjournaling--

PartIII

Howtouseajournalfordisasterrecovery

Journals,likemirroring,canbeusedasprotectionagainstlossofdatafromadiskcrash.Thetrade-offisthis:Journalingusesalotlessdiskspacethanmirroring,sinceitisonlyprotectingfiles(whichiswheremostofthesystemactivity,i.e.datachanges,takesplace).However,thisisalsoadisadvantagebecause,again,onlyfilesareprotected.

Inaddition,set-upandrecoveryrequireafewmoremanualsteps.Formaximumprotection,usethefollowingsteps.

Journalset-upandsaveprocess

Everycriticalfile(whichismostfiles)shouldbejournaled.Youcanjournalmultiplefilestothesamejournal,butusecautionwhendoingsobecausethiswillintroduceanotherlevelofcomplexity(orconfusion,asthecasemaybe).Thefollowingdescribesthesteps...

requiredtosetupjournalingforasinglefile:

Setupjournal(s)asdescribedinPartIandPartII.PutjournalandjournalreceiversinadifferentASPthanthefiletheyareprotecting.IfyouhaveneverusedASPsbefore,nowisagoodtimetostart.YoucankeepitsimpleandjustdedicateasmallASPforjournalingonly.Thatwayyouensurethatthefileanditsassociatedjournalarestoredondifferentdiskunits.Asanaddedbonus,usingaseparateASPforjournalswillimproveperformance,comparedwithputtingjournalsandfileinthesameASP.

Savethefileeachnight.Youcanstretchthisouttoeveryothernightoronceaweek,buttokeepjournalreceiversfromgettingtoobig,itisbesttosavethefileeachnight.

Createandattachanewjournalreceiver.Thisgivesthejournalafreshstartthenextday.

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Savetheprevious(nowdetached)journalreceiver.Thisstepisoptional.Itgivesyouanextralayerofprotection.Shouldanythinghappentothefileonthesavedmedia,youcouldreconstructthefilefromthepreviousnight'ssaveandthesavedjournalreceiver.

Deletethepreviousjournalreceiver.Thisistheonlywayto"clear"theentriesinthereceiver.

MoreInformation

MovingalibraryfromoneASPtoanother

Wanttospeedupyournightlybackup?Usesavefiles

[IMAGE]

Recoveryprocedure

Afteradiskcrashorotherfailurethatrendersafileunusable,

usethefollowingstepstorecoverthatfile:

Restorethesavedfile.Usethemostrecentsavemedia.

Applyjournaledchangestotherestoredfile.UsetheApplyJournalChanges(APYJRNCHG)commandtoperformthisstep.

Aftercompletion,thefilewillbeinthesamestatethatitwaswhenthediskcrashed.Thisassumes,ofcourse,thatthejournalandthejournalreceiverwerestoredinadifferentASP.Note:TheparameterdefaultsoftheAPYJRNCHGcommandaresetupfordisasterrecovery,soyouprobablywon'tneedtochangethem.

RestoreobjectsinthecorrectorderSimilartowhenyouusetriggersorreferentialintegrity,whenyouusejournalingandperformarestoreyoumustensurethatcertainobjectsarerestoredintheproperorder

sothatjournalingcanbere-establishedautomatically.Whenyouneedtorestoreafilethatisjournaled,alongwithitsassociatedobjects(i.e.,logicalfiles,journalandjournalreceivers),

usethefollowingorder:

Restorethejournalobjectfirst(butnotthereceivers)

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Restorethephysicalfileorfiles

Restoretheanyassociatedlogicalfiles

Restorethejournalreceivers

Tomakethingssimple,putthejournalandreceiversinthesamelibraryasthefiles.Whenconfiguredthisway,thesystemwillautomaticallyrestorethemintheproperorderifyourestoretheentirelibrary(usingtheRSTLIBcommand).Iftheyareindifferentlibrariesandyoudonotrestoretheobjectsintheaboveorder,youwillhavetore-establishjournalingmanually,whichmayincludere-attachingreceiversand/orrestartingjournalingforfiles.

Note:Therestoreprocedurejustdiscussedisonlyforwhenyouneedtorestoreafileanditsassociatedjournalandreceivers.

Intherecoveryprocedurediscussedearlier,weassumedthatthejournalsandreceiversdidnothavetoberestoredbecausetheywereinanotherASPandwerenotaffectedbythediskcrash.

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Theinsandoutsofjournaling--

PartIV

Fourtipsforreducingjournalsize

Inthefirstthreepartsofthisseriesonjournalingwediscussedhowtomanageandusejournalstomaintaindataintegrity,butwedidn'tgivemuchthoughttothephysicalsizeoftheobjectsinvolvedinjournaling.Let'snowtakeaquicklookathowyoucanhelpminimizejournalandjournalreceiversizes.

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Journalobjectsareonlydefinitionalobjects;thatis,theycontainonlyadefinitionandnotexpandingamountsofdata.Therefore,journalobjectsmaintainaconstantandveryminimalsize.

Whatcanwedoaboutobjectsizes?Plenty.Ifyourecall,journalentriesarewrittentojournalreceivers,sojournalreceiversarealwaysexpanding.Thereareseveralwaystoreducethesizeofyourjournalreceivers.Mosthavetodowithomittingcertaintypesofentriesoreliminatingsome...oftheinformationintheentries.

IfDASDistightonyoursystem,herearesomethingsyoucandotocutdownonspacerequirementsforjournalsandjournalreceivers:

MoreInformation

Howtouseajournalfordisasterrecovery

Managingjournalreceivers

Theinsandoutsofjournaling--PartI

SpecifyOMTJRNE(*OPNCLO)ontheSTRJRNPFcommandwhenyoustartthejournalingforafile.

Bydefault,eachtimeaprogramopensandclosesajournaledfile,thesystemrecords"OP"and"CL"entries.

ByspecifyingOMTJRNE(*OPNCLO),youwillblockthesystemfromrecordingthoseentries(whichareusuallyusedonlyforsecurityauditingpurposes).

SpecifyIMAGES(*AFTER)ontheSTRJRNPFcommandtorecordonlyafterimages.

Youcanconfigurejournalingtorecordbothabeforeimageandanafterimageofanyrecordthatisupdated.Thatis,thejournalrecordsacopyoftheoriginalrecordbeforeitisactuallyupdatedinthefile(beforeimage)andacopyoftherecordasitappearsaftertheupdate(afterimage).

Thedefaultisafterimagesonly,andthatiswhatyoushoulduseunlessyouhaveaspecificneedforthebeforeimages.

ForthedisasterrecoveryprocesswediscussedinPartIIIofthisseries,onlyafterimagesarenecessary.Commitmentcontrolrequiresbeforeimages,butthesystemwillstartrecordingthemautomaticallywhencommitmentcontrolisstartedandwillceaserecordingthemwhencommitment

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controlisended.YoucanuseIMAGES(*BOTH)tomanuallyrecordbothbeforeimagesandafterimages.

UseRCVSIZOPT(*RMVINTENT)ontheCHGJRNorCRTJRNcommands.

Thiscausesthesystemtoautomaticallyremoveinternalentriesoncetheyarenolongerneeded.Forexample,duringIPLthesystemlogsanentrytoeachjournal,indicatingwhetherthesystemisIPL-ingafteranormalorabnormalend.

AfterthenextIPL,theentriesassociatedwiththepreviousIPLarenolongerneeded,andthesystemwillautomaticallydeletethemifyouspecifyRCVSIZOPT(*RMVINTENT)ontheCHGJRNcommandwhenyoucreatethejournal.(YoucanalsousetheCHGJRNcommandtochangeanexistingjournal.)Note:Don'tlookforanymiracleshere.Theseinternalentriesrepresentatinyfractionofalltheentriesofannormalactivejournal.

UseRCVSIZOPT(*MINFIXLEN)ontheCHGJRNorCRTJRNcommands.

When*MINFIXLENisused,thesystemshortensjournalentriesbynotwritingoutthejob,programanduserprofileinformationthatnormallyaccompanieseachjournalentry.ThistrickcanadduptobigDASDsavings,since46byteswillbeshavedoffofeachentry.Note:Thejob,programanduserprofileinformationisusedforsecurityauditingpurposes,

soyoudonotsacrificeanydata-recoveryabilitiesbynothavingtheminthejournalentries.

Onafinalnote,rememberthatthesetechniquesarenotmutuallyexclusive.Youcanuseanycombinationofthemtofityourneeds.