翻译文献-使用调度器操作任务

外文原文USINGTHESCHEDULERTOAUTOMATETASKSASANORACLEDATABASEADMINISTRATOR,YOUMIGHTFINDTHATANINORDINATEAMOUNTOFYOURTIMEISSPENTPERFORMINGROUTINETASKSUNFORTUNATELY,ROUTINETASKSCOMEWITHTHETERRITORY,ANDTHATISUNLIKELYTOCHANGEINTHEFORESEEABLEFUTUREHANDLINGTHESEROUTINETASKSMANUALLYISANINVITATIONFORPROBLEMSMISTAKESCANBEMADE,OREVENWORSE,THETASKSWILLBEFORGOTTENANDNOTRUNATALLTORESOLVETHISDILEMMA,ORACLEDATABASE10GORACLE10GINTRODUCEDTHEORACLESCHEDULER,ANEWFEATURETHATMAKESTHESCHEDULINGOFROUTINETASKSASIMPLEMATTERTHEORACLESCHEDULERISAMAJORADVANCEMENTOVERTHEOLDDBMS_JOBSCHEDULINGSYSTEMFOUNDINPREVIOUORACLEVERSIONSITCORRECTSMANYOFTHENAGGINGIDIOSYNCRASIESWHILEADDINGPOWERFULNEWFEATURESSUCHASTHECALENDARINGSYNTAX,AFLEXIBLEMETHODOFDEFININGREPEATINTERVALSFORSCHEDULERJOBSINTHISCHAPTER,YOUWILLLEARNHOWTHESCHEDULERWORKSANDHOWTOCREATEANDMANAGESCHEDULERELEMENTSFIRST,YOUWILLGETANOVERVIEWOFTHETERMINOLOGYANDCOMPONENTSTHATMAKEUPTHESCHEDULERYOUWILLLEARNTHEUNDERLYINGARCHITECTUREOFTHESCHEDULERANDHOWALLTHEPIECESFITTOGETHERNEXT,YOUWILLLEARNABOUTSCHEDULERJOBSANDHOWTOCREATEANDMANAGETHEMYOUWILLALSOLEARNABOUTJOBGROUPSANDHOWTHEYCANBEUSEDTOSIMPLIFYTHEMANAGEMENTOFJOBS,ASWELLASTOPRIORITIZEJOBEXECUTIONYOUWILLALSOLEARNABOUTSCHEDULERPROGRAMS,WHICHDEFINETHEWORKTHATWILLBEPERFORMEDYOULLLEARNTOCREATEANDMANAGESCHEDULES,WHICHDEFINEWHENJOBSWILLBERUNANDHOWOFTENTHEYWILLBEREPEATEDYOULLLEARNHOWTODEFINECOMPLEXREPEATINTERVALSUSINGORACLESNEWALENDARINGSYNTAXNEXT,YOUWILLLEARNABOUTWINDOWSANDWINDOWGROUPS,WHICHALLOWYOUTOSWITCHRESOURCEPLANSBASEDONASCHEDULEAND,LASTLY,YOUWILLLEARNABOUTTHESCHEDULERVIEWSTHATAREAVAILABLETOYOUSCHEDULEROVERVIEWTHEMAINFUNCTIONALITYOFANYENTERPRISESCHEDULINGSYSTEMISTHEABILITYTOSCHEDULETASKSTOEXECUTEATASPECIFICDATEANDTIMETHESECANBERECURRINGTASKSTHATRUNATPRESETINTERVALSORONETIMETASKSSETTOEXECUTEIMMEDIATELYORATSOMEPOINTINTHEFUTURETOACHIEVETHISFUNCTIONALITY,THESCHEDULERUSESSEVERALDISTINCTCOMPONENTSTOSPECIFYSCHEDULEDTASKSINSTRUCTSTHESCHEDULERTORUNASPECIFICPROGRAMATASPECIFICTIMEONASPECIFICDATEPROGRAMPROGRAMCONTAINSTHECODEORAREFERENCETOTHECODETHATNEEDSTOBERUNTOACCOMPLISHATASKITCANALSOCONTAINPARAMETERSTHATSHOULDBEPASSEDTOTHEPROGRAMATRUNTIMEAPROGRAMCANBESTOREDASANINDEPENDENTOBJECTTHATCANBEREFERENCEDBYMANYJOBSSCHEDULESASCHEDULECONTAINSASTARTDATE,ANOPTIONALENDDATE,ANDAREPEATINTERVALWITHTHESEELEMENTS,ANEXECUTIONSCHEDULECANBECALCULATEDASCHEDULECANBESTOREDASANINDEPENDENTOBJECTTHATCANBEREFERENCEDBYMANYJOBSWINDOWSAWINDOWIDENTIFIESARECURRINGBLOCKOFTIMEDURINGWHICHASPECIFICRESOURCEPLANSHOULDBEENABLEDTOGOVERNRESOURCEALLOCATIONFORTHEDATABASEFORINSTANCE,THEWEEKENDMAYBECLASSIFIEDASAMAINTENANCEWINDOW,ANDYOUCANENABLEARESOURCEPLANTHATALLOCATESTHEBULKOFTHESYSTEMRESOURCESTOADMINISTRATIVEUSERSJOBGROUPSJOBGROUPISALOGICALMETHODOFCLASSIFYINGJOBSWITHSIMILARCHARACTERISTICSJOBGROUPSDEFINESPECIFICCHARACTERISTICSTHATWILLBEINHERITEDBYALLJOBSASSIGNEDTOTHEGROUPTHEYALSOSIMPLIFYMANAGEMENTBYALLOWINGCOLLECTIONSOFJOBSTOBEMANIPULATEDASONEOBJECTWINDOWGROUPSWINDOWGROUPISALOGICALMETHODOFGROUPINGWINDOWSTHEYSIMPLIFYTHEMANAGEMENTOFWINDOWSBYALLOWINGTHEMEMBERSOFTHEGROUPTOBEMANIPULATEDASONEOBJECTUNLIKEJOBGROUPS,WINDOWGROUPSDONTSETDEFAULTCHARACTERISTICSFORWINDOWSTHATBELONGTOTHEGROUPTHESEBASICCOMPONENTSCOMPRISETHEBULKOFORACLESSCHEDULERFACILITYTHEIRDESIGNENCOURAGESBUILDINGFLEXIBLE,REUSABLECOMPONENTSSHAREDBYMANYSCHEDULEDJOBSTHESCHEDULERALSOOFFERSAPOWERFULANDFLEXIBLECALENDARINGSYNTAXTHATISUSEDTOSPECIFYRECURRINGTASKEXECUTIONSTHISNEWSYNTAXALLOWSFORTHESPECIFICATIONOFCOMPLEXDATEANDTIMEREQUIREMENTSITALSOELIMINATESMANYOFTHESHORTCOMINGSOFDBMS_JOBSUCHASSCHEDULECREEPWHERETHESTARTTIMEOFATASKWASDIRECTLYAFFECTEDBYTHESTARTTIMEOFTHEPREVIOUSEXECUTIOOFTHATTASKLASTLY,THESCHEDULERALLOWSTHEEXECUTIONOFNONORACLERELATEDPROGRAMSANDSCRIPTSTHISMEANSTHATTHESCHEDULERCANBEUSEDNOTONLYTOEXECUTESQLANDPL/SQL,BUTALSOOPERATINGSYSTEMEXECUTABLEPROGRAMSTHEREFORE,MOSTALLOFYOURTASKSCANBESCHEDULEDINACOMMONPLACESCHEDULERARCHITECTUREUNDERSTANDINGHOWTOUSETHESCHEDULERBEGINSWITHUNDERSTANDINGTHEUNDERLYINGARCHITECTUREUPONWHICHTHESCHEDULERFUNCTIONALITYISBUILTTHISISNOTTOSAYTHATYOUHAVETOBEABLETONAMEEVERYLOCKINGMECHANISMANDMEMORYSTRUCTUREUSEDINTHESCHEDULER,ANYMORETHANAPERSONNEEDSTOKNOWTHEIGNITIONSEQUENCEOFTHEIRCARINORDERTODRIVEITRATHER,ITIMPLIESTHATAHIGHLEVELKNOWLEDGEOFTHEUNDERLYINGSCHEDULERPROCESSESWILLHELPYOUCREATEMORELOGICALSCHEDULEROBJECTSANDENABLEYOUTOTROUBLESHOOTPROBLEMSASSOCIATEDWITHTHESCHEDULERINTHESESECTIONS,YOUWILLLEARNABOUTTHEJOBTABLE,WHICHHOUSESALLTHEACTIVEJOBSWITHINTHEDATABASETHEJOBCOORDINATOR,AKEYORACLEPROCESSTHATENSURESTHATJOBSAREBEINGRUNONSCHEDULEJOBSLAVES,PROCESSESTHATCARRYOUTTHEEXECUTIONOFJOBSUNDERTHEGUIDANCEOFTHEJOBCOORDINATOR_THEARCHITECTUREINREALAPPLICATIONCLUSTERRACENVIRONMENTSANDHOWITDIFFERSONLYSLIGHTLYFROMASTANDALONEDATABASEENVIRONMENTTHEJOBCOORDINATORTHEJOBCOORDINATORISANORACLEBACKGROUNDPROCESSWITHTHERESPONSIBILITYOFENSURINGTHATJOBSARERUNONSCHEDULETHEJOBCOORDINATORREGULARLYQUERIESTHEJOBTABLEANDCOPIESJOBINFORMATIONTOAMEMORYCACHEFORIMPROVEDPERFORMANCEWHENTHEJOBISEXECUTEDTHEORACLEDATABASEITSELFMONITORSJOBSCHEDULESANDSTARTSTHEJOBCOORDINATORPROCESSIFITISNOTALREADYSTARTEDWHENAJOBNEEDSTOBEEXECUTEDTHEJOBCOORDINATORPULLSTHEJOBINFORMATIONFROMTHEMEMORYCACHEANDPASSESITTOAJOBSLAVEDESCRIBEDINTHENEXTSECTIONPROCESSFOREXECUTIONTHEJOBCOORDINATORCONTROLSALLASPECTSOFTHEJOBSLAVEPOOLOFPROCESSES,SOITCANREMOVEDORMANTSLAVEPROCESSESANDSPAWNNEWPROCESSESASNEEDEDTOMEETTHENEEDSOFTHESCHEDULERTHEJOBSLAVEPROCESSESJOBSLAVEPROCESSESARETASKEDWITHCARRYINGOUTTHEEXECUTIONOFJOBPROGRAMSASSIGNEDTOTHEMBYTHEJOBSCHEDULERWHENAJOBSLAVERECEIVESTHEJOBINFORMATIONFROMTHECOORDINATOR,ITSETSTOWORKCOLLECTINGALLTHEMETADATATHATITNEEDSTOCARRYOUTTHEREQUESTTHISMETADATAINCLUDESTHINGSSUCHASTHEPROGRAMARGUMENTSANDPRIVILEGEINFORMATIONRACCONSIDERATIONSTHESCHEDULERARCHITECTUREINANORACLEREALAPPLICATIONCLUSTERRACENVIRONMENTISTHESAMEASINASTANDALONEINSTANCE,WITHTHEFOLLOWINGEXCEPTIONS_EACHINSTANCEINTHECLUSTERWILLHAVEITSOWNJOBCOORDINATOR_THEJOBCOORDINATORSCANCOMMUNICATEWITHONEANOTHERTOSHAREINFORMATION_JOBSCANBEDEFINEDWITHASERVICEAFFINITYTHEYSHOULDRUNONASPECIFICSERVICEASOPPOSEDTOANINSTANCEAFFINITYTHEYSHOULDRUNONASPECIFICINSTANCEIFAJOBISASSIGNEDTOASERVICECONSISTINGOFTWOINSTANCES,EVENIFONEINSTANCEISDOWN,THEOTHERCANEXECUTETHEJOBNORMALLYASIDEFROMTHESEEXCEPTIONS,THESCHEDULERARCHITECTUREINARACENVIRONMENTISTHESAMEASDESCRIBEDPREVIOUSLYCOMMONADMINISTRATIONTOOLSTHEORACLESCHEDULERISIMPLEMENTEDTHROUGHAPL/SQLPACKAGENAMEDDBMS_SCHEDULERTHISPACKAGEOFFERSACOLLECTIONOFPROCEDURESTHATAREUSEDTOCREATEANDMANAGESCHEDULEROBJECTSJOBS,PROGRAMS,SCHEDULES,WINDOWS,JOBGROUPS,ANDWINDOWGROUPSEACHOFTHESEOBJECTTYPESWILLBECOVEREDTHOROUGHLYINTHISCHAPTERMOSTOFTHEPROCEDURESINTHEDBMS_SCHEDULERPACKAGEARESPECIFICTOACERTAINOBJECTTYPETHEOBJECTTYPECANBEDERIVEDFROMTHENAMEOFTHEPROCEDUREFOREXAMPLE,THCREATE_PROGRAMPROCEDUREISOBVIOUSLYSPECIFICTOPROGRAMOBJECTSHOWEVER,BECAUSEALLSCHEDULEROBJECTSSHARESOMECOMMONATTRIBUTES,THEREAREALSOPROCEDURESTHATWORKWITHANYSCHEDULEROBJECTTYPEBECAUSETHESEPROCEDURESPLAYANIMPORTANTROLEINTHEMANAGEMENTOFSCHEDULEROBJECTS,THEYWARRANTTHOROUGHCOVERAGEHOWEVER,DUETOTHEIR“GLOBAL”NATURE,THEYWILLBECOVEREDINTHISSECTION,SEPARATEFROMANYSPECIFICOBJECTTYPEUSINGTHEDISABLEPROCEDUREWHENASCHEDULEROBJECTISDISABLED,ITISINELIGIBLEFORUSEBYTHESCHEDULERDISABLINGASCHEDULEROBJECTISACCOMPLISHEDBYSETTINGTHEOBJECTSENABLEDATTRIBUTETOFALSETODISABLEANOBJECT,THEDBMS_SCHEDULERDISABLEPROCEDUREISUSEDTHISPROCEDUREACCEPTSTWOPARAMETERSNAMEANDFORCETHENAMEPARAMETERDESIGNATESONEOFTHEFOLLOWING_THENAMEOFONESPECIFICOBJECT_ACOMMASEPARATEDLISTOFOBJECTSTHEFORCEPARAMETERISABOOLEANTRUEORFALSEVALUETHATTELLSTHEPROCEDUREHOWTOHANDLETHEREQUESTIFDEPENDENCIESEXISTTHEDEFAULTVALUEISFALSETHEREARETWOSITUATIONSTHATCOULDBECLASSIFIEDASDEPENDENCIESAJOBOBJECTTHATREFERENCESAPROGRAMOBJECTISCONSIDEREDTOBEDEPENDENTONTHATOBJECT_IFANINSTANCEOFANOBJECTISCURRENTLYRUNNINGFOREXAMPLE,AWINDOWISOPENORAJOBISRUNNING,THEREMAYBEADEPENDENCYISSUEIFANYDEPENDENCIESAREFOUND,THEVALUEOFTHEFORCEPARAMETERWILLDETERMINETHEULTIMATEOUTCOMEOFTHEDISABLEPROCEDURESETTINGATTRIBUTESYOUMIGHTBESURPRISEDTOFINDTHATTHEDBMS_SCHEDULEPACKAGEDOESNOTHAVEANALTERPROCEDUREOFANYKINDTHISISBECAUSESCHEDULEROBJECTSARECOLLECTIONSOFATTRIBUTESTOMAKEACHANGETOANOBJECTREQUIRESSETTINGITSATTRIBUTESTHEREFORE,TOALTERASCHEDULEROBJECT,THEDBMS_SCHEDULERSET_ATTRIBUTEANDDBMS_SCHEDULERSET_ATTRIBUTE_NULLPROCEDURESAREUSEDINTHEFOLLOWINGSECTIONS,YOUWILLLEARNTOUSETHESEPROCEDURESWITHALLTYPESOFSCHEDULEROBJECTSTHESET_ATTRIBUTEPROCEDURESETSANATTRIBUTEFORANYTYPEOFSCHEDULEROBJECTTHESET_ATTRIBUTE_NULLPROCEDURE,ONTHEOTHERHAND,SETSANYATTRIBUTETONULLFORANYTYPEOFSCHEDULEROBJECTTHISISUSEFULFOR“UNSETTING”ANATTRIBUTETHEONLYATTRIBUTETHATCANNOTBEALTEREDFORANYTYPEOFSCHEDULEROBJECTISTHENAMEOFTHEOBJECTWHENTHEATTRIBUTESONANOBJECTARECHANGED,ORACLEWILLATTEMPTTODISABLETHEOBJECTBEFOREMAKINGTHECHANGESWHENTHEATTRIBUTEHASBEENSUCCESSFULLYALTERED,ORACLEWILLREENABLETHEOBJECTAUTOMATICALLYIFTHESET_ATTRIBUTEPROCEDUREFAILS,THEOBJECTWILLREMAINDISABLEDANDANERRORMESSAGEISRETURNEDUSINGTHESET_ATTRIBUTEPROCEDUREDOESNOTAFFECTINSTANCESOFTHEOBJECTTHATARECURRENTLYEXECUTINGCHANGESMADEWILLONLYAFFECTFUTUREINSTANTIATIONSOFTHEOBJECTTHESET_ATTRIBUTEPROCEDUREACCEPTSTHREEPARAMETERSNAMETHENAMEOFTHESCHEDULEROBJECTATTRIBUTETHENAMEOFTHEATTRIBUTETOBECHANGEDVALUETHENEWVALUEFORTHEATTRIBUTETHEPROCEDUREISOVERLOADEDTOACCEPTAVALUEOFANYAPPLICABLEDATATYPE,SONOCONVERSIONISNECESSARYWHENSETTINGVALUESFORDIFFERENTDATATYPESTHESET_ATTRIBUTE_NULLPROCEDUREACCEPTSONLYTWOPARAMETERSNAMETHENAMEOFTHESCHEDULEROBJECTATTRIBUTETHENAMEOFTHEATTRIBUTE,WHICHSHOULDBESETTONULLINTHELASTSECTION,YOULEARNEDTHATANOBJECTWASCONSIDEREDENABLEDWHENTHEENABLEDATTRIBUTEWASSETTOAVALUEOFTRUETHEREFORE,YOUCANENABLEORDISABLEANOBJECTBYUSINGTHESET_ATTRIBUTEPROCEDURE,ASSHOWNHEREUSINGSCHEDULERJOBSASCHEDULERJOBDEFINESASPECIFICPROGRAMTOBEEXECUTED,THEARGUMENTSORPARAMETERSTOBEPASSEDTOTHEPROGRAM,ANDTHESCHEDULEDEFININGWHENTHEPROGRAMSHOULDBEEXECUTEDITALSOSPECIFIESOTHERCHARACTERISTICSSUCHASLOGGINGOPTIONS,JOBPRIORITY,ANDSOONMANYOFTHESECHARACTERISTICSAREEXPLICITLYSETATJOBCREATIONTIMETHROUGHTHECREATE_JOBPROCEDUREHOWEVER,OTHERSAREINHERITEDFROMTHEJOBCLASSTOWHICHTHEJOBISASSIGNEDIFAJOBISNOTEXPLICITLYASSIGNEDTOAJOBCLASS,THESECHARACTERISTICSWILLBEINHERITEDFROMAJOBCLASSNAMEDDEFAULT_JOB_CLASSINTHEFOLLOWINGSECTIONS,YOUWILLLEARNHOWTOADMINISTERTHEVARIOUSASPECTSOFSCHEDULERJOBSYOUWILLLEARNTOCREATE,COPY,ANDALTERJOBSTOACHIEVEYOURSCHEDULINGNEEDSYOUWILLLEARNHOWTORUNJOBSANDHOWTOSTOPJOBSTHATARERUNNINGYOUWILLLEARNHOWTOENABLEANDDISABLEJOBS,ANDFINALLY,HOWTODROPJOBSTHATARENOLONGERNEEDEDCREATINGJOBSSCHEDULERJOBSCANBECREATEDBYUSINGTHEDBMS_SCHEDULERCREATE_JOBPROCEDUREASYOUWILLRECALL,AJOBCOMBINESAPROGRAMANDASCHEDULEFOREXECUTIONOFTHATPROGRAMTHEREFORE,THESEARETHEELEMENTSTHATYOUMUSTDEFINEWHENCREATINGANEWJOBDEPENDINGONTHEPROGRAMTHATTHEJOBUSES,YOUMAYALSONEEDTOSETJOBARGUMENTSTHESEAREPARAMETERSTHATWILLBEPASSEDTOTHEPROGRAMATEXECUTIONTIMEJOBARGUMENTSCANBESETBYUSINGTHESET_JOB_ARGUMENTAND/ORSET_JOB_ANYDATA_VALUEPROCEDURESINTHEDBMS_SCHEDULERPACKAGEJOBSALSOHAVEJOBATTRIBUTESTHATCONTROLCERTAINBEHAVIORSOFTHEJOBMANYOFTHESECANBESETTHROUGHTHECREATE_JOBPROCEDURE,WHILEOTHERSAREINHERITEDFROMTHEJOBCLASSTOWHICHTHEJOBISASSIGNEDORFROMTHEDEFAULT_JOB_CLASSCLASS,ASMENTIONEDPREVIOUSLYFOREXAMPLE,JOBATTRIBUTESSUCHASTHEJOB_TYPE,JOB_ACTION,ANDREPEAT_INTERVALCANALLBEDEFINEDATJOBCREATIONTIMEOTHERATTRIBUTESSUCHASMAX_FAILURES,LOGGING_LEVEL,ANDJOB_PRIORITYAREINHERITEDFROMTHEJOBCLASSAJOBISSTOREDLIKEANYOTHERDATABASEOBJECT,SOITISVITALTHATAVALIDOBJECTNAMEISUSEDWHENCREATINGJOBSTHEJOBNAMEMUSTALSOBEUNIQUEWITHINTHESCHEMAINWHICHITISCREATEDLIKEOTHERDATABASEOBJECTS,JOBSCANBECREATEDINADIFFERENTSCHEMABYPREFIXINGTHEJOBNAMEWITHASCHEMANAMEFOREXAMPLE,SPECIFYINGAJOBNAMEOFBUTERTBSTATS_JOBWOULDCAUSETHEJOBTOBECREATEDINTHEBUTERTBSCHEMAINTHEFOLLOWINGSECTIONS,YOUWILLLEARNWHICHATTRIBUTESDEFINEASCHEDULERJOBYOUWILLALSOLEARNHOWTOADMINISTERALLASPECTSOFSCHEDULERJOBOBJECTSJOBATTRIBUTESSCHEDULERJOBSHAVEASPECIFICSETOFATTRIBUTESTHATYOUCANSETTODEFINETHECHARACTERISTICSOFTHEJOBTHESEATTRIBUTESCANBESETATJOBCREATIONTIMETHROUGHTHEFOLLOWINGCREATE_JOBPROCEDUREPARAMETERSJOB_NAMETHEJOB_NAMEPARAMETERSPECIFIESTHENAMEASSIGNEDTOTHENEWJOBBECAUSEJOBSARESTOREDLIKEANYOTHERDATABASEOBJECT,STANDARDORACLENAMINGREQUIREMENTSAREENFORCEDFORJOBSTHISMEANSTHATTHEJOBNAMEMUSTNOTONLYBEAVALIDORACLEOBJECTNAME,ITMUSTALSOBUNIQUEWITHINTHESCHEMAJOB_TYPETHEJOB_TYPEPARAMETERSPECIFIESTHETYPEOFJOBTHATWILLBECREATEDTHISISAREQUIREDPARAMETERANDCANNOTBEEXCLUDEDITCANBEANYONEOFTHEFOLLOWINGPLSQL_BLOCKTHEJOBWILLEXECUTEANANONYMOUSPL/SQLBLOCKANONYMOUSPL/SQLBLOCKJOBSDONOTACCEPTJOBORPROGRAMARGUMENTS,SOTHENUMBEROFARGUMENTSATTRIBUTEMUSTBESETTO0STORED_PROCEDURETHEJOBWILLEXECUTEAPL/SQLSTOREDPROCEDUREBYUSINGPL/SQLSEXTERNALPROCEDUREFEATURE,THEPL/SQLPROCEDURECOULDBEAWRAPPERTOCALLAJAVASTOREDPROCEDUREORANEXTERNALCROUTINEEXECUTABLETHEJOBWILLEXECUTEAPROGRAMTHATISEXTERNALTOTHEDATABASEANEXTERNALJOBISANYPROGRAMTHATCANBEEXECUTEDFROMTHEOPERATINGSYSTEMSCOMMANDLINEANYDATAARGUMENTSARENOTSUPPORTEDWITHAJOBORPROGRAMTYPEOFEXECUTABLEUSINGJOBCLASSESAJOBCLASSISACONTAINEROBJECTFORTHELOGICALGROUPINGOFJOBSINTOALARGERUNITCLASSIFYINGJOBSINTHISMANNEROFFERSSEVERALADVANTAGES_FROMANADMINISTRATIVEPERSPECTIVE,ITISEASIERTOMANAGEASMALLNUMBEROFJOBGROUPSTHANALARGENUMBEROFINDIVIDUALJOBSCERTAINJOBCHARACTERISTICSCANBEASSIGNEDATTHEGROUPLEVELANDWILLBEINHERITEDBYALLJOBSWITHINTHEGROUPCERTAINADMINISTRATIVEPROCEDURESWILLALSOOPERATEATTHEGROUPLEVEL,MAKINGADMINISTRATIVEFUNCTIONSEASIER_JOBCLASSESCANBEASSIGNEDTOARESOURCECONSUMERGROUPTHISALLOWSYOUTOCONTROLRESOURCEALLOCATIONFORALLJOBSWITHINTHEGROUP_JOBSCANBEPRIORITIZEDWITHINTHEJOBCLASSTHISGIVESYOUMORECONTROLOVERWHICHJOBSSHOULDTAKEPRECEDENCEINCASEOFACONFLICTFOREXAMPLE,IFACONFLICTOCCURS,THEJOB_PRIORITYATTRIBUTEOFEACHJOBWILLBEEVALUATEDAJOBWITHAVALUEOFHIGHTAKESPRIORITYOVERAJOBWITHAVALUEOFLOWALLJOBSMUSTBELONGTOEXACTLYONEJOBCLASSANYJOBNOTEXPLICITLYASSIGNEDTOAJOBCLASSWILLBELONGTOTHEDEFAULT_JOB_CLASSCLASS,ANDTHEYWILLINHERITTHECHARACTERISTICSOFTHATJOBCLASSINTHEFOLLOWINGSECTIONS,YOUWILLLEARNTOCREATEANDADMINISTERJOBCLASSESJOBCLASSPARAMETERSJOBCLASSESHAVEASPECIFICSETOFATTRIBUTESTHATYOUCANSETTODEFINETHECHARACTERISTICSOFTHECLASSTHESEATTRIBUTESWILLBEINHERITEDBYALLJOBSASSIGNEDTOTHEJOBCLASS,THEREBYSAVINGYOUTHEWORKOFSETTINGTHEMINDIVIDUALLYONEACHJOBTHEAVAILABLEATTRIBUTEPARAMETERSAREDESCRIBEDHEREJOB_CLASS_NAMETHEJOB_CLASS_NAMEPARAMETERUNIQUELYIDENTIFIESTHEJOBCLASSINTHESYSSCHEMATHENAMEHASTOBEUNIQUEINTHESYSSCHEMARESOURCE_CONSUMER_GROUPTHERESOURCE_CONSUMER_GROUPPARAMETERASSOCIATESTHEJOBGROUPWITHASPECIFICCONSUMERGROUPALLJOBSASSIGNEDTOTHEJOBGROUPWILLAUTOMATICALLYBEGOVERNEDBYTHISCONSUMERGROUPSERVICETHESERVICEPARAMETERSPECIFIESTHESERVICETOWHICHTHEJOBCLASSBELONGSTHISMEANSTHAT,INARACENVIRONMENT,THEJOBSINTHISCLASSWILLHAVEAFFINITYTOTHEPARTICULARSERVICESPECIFIEDTHEREFORE,THEYWILLRUNONLYONTHOSEDATABASEINSTANCESTHATAREASSIGNEDTOTHESPECIFICSERVICEIFTHISATTRIBUTEISNOTSET,THEDEFAULTSERVICEWILLBEUSED,MEANINGTHATTHEJOBSHAVENOSERVICEAFFINITYANDCANBERUNBYANYINSTANCEWITHINTHECLUSTERIFTHESERVICEPARAMETERISSPECIFIED,THERESOURCE_CONSUMER_GROUPATTRIBUTECANNOTBESETTHEYAREMUTUALLYEXCLUSIVELOGGING_LEVELTHEORACLESCHEDULERCANOPTIONALLYMAINTAINJOBLOGSOFALLJOBACTIVITIESJOBLOGGINGISDETERMINEDBYTHESETTINGOFTHELOGGING_LEVELATTRIBUTEOFTHEJOBCLASSTHELOGGING_LEVELPARAMETERSPECIFIESHOWMUCHJOBINFORMATIONILOGGEDTHEREARETHREEVALIDSETTINGSFORTHISATTRIBUTEDBMS_SCHEDULERLOGGING_OFFNOLOGGINGWILLBEPERFORMEDFORANYJOBSINTHISCLASSDBMS_SCHEDULERLOGGING_RUNSDETAILEDINFORMATIONWILLBEWRITTENFORALLRUNSOFEACHJOBINTHECLASSDBMS_SCHEDULERLOGGING_FULLDETAILEDINFORMATIONWILLBEWRITTENFORALLRUNSOFEACHJOBINTHECLASS,ANDEVERYOPERATIONPERFORMEDONANYJOBINTHECLASSCREATE,ENABLE,DROP,ANDSOONWILLBELOGGEDNOTETHATTHEVALIDVALUESFORTHISPARAMETERAREALLCONSTANTSDEFINEDWITHINTHEDBMS_SCHEDULERPACKAGETHEREFORE,THEYMUSTBEREFERENCEDEXACTLYASSHOWN,WITHNOQUOTESAROUNDTHEMLOG_HISTORYTHELOG_HISTORYPARAMETERDETERMINESTHENUMBEROFDAYSLOGGEDINFORMATIONSHOULDBERETAINEDTHEDEFAULTVALUEIS30DAYSVALIDVALUESARE1TO999WHENRECORDSHAVEEXCEEDEDTHISAGE,THESCHEDULERWILLAUTOMATICALLYPURGETHEMCOMMENTSTHECOMMENTSPARAMETERSPECIFIESANOPTIONALCOMMENTABOUTTHEJOBCLASSUSINGSCHEDULERPROGRAMSAPROGRAMDEFINESTHEACTIONTHATWILLOCCURWHENAJOBRUNSITCANBEAPL/SQLBLOCK,ASTOREDPROCEDURE,ORANOPERATINGSYSTEMEXECUTABLEINTHEPREVIOUSSECTION,YOULEARNEDTODEFINEAPROGRAMWITHINTHECONFINESOFTHECREATE_JOBPROCEDUREHOWEVER,PROGRAMSCANALSOBECREATEDASINDEPENDENTOBJECTSTHATCANBEREUSEDBYMANYDIFFERENTJOBSANDBECAUSEPROGRAMSCANALSOACCEPTARGUMENTS,THEYOFFERFLEXIBILITYANDENCOURAGEREUSEINTHEFOLLOWINGSECTIONS,YOUWILLLEARNTHEDIFFERENTATTRIBUTESTHATDEFINEASCHEDULERPROGRAMOBJECTYOUWILLLEARNHOWTOCREATENEWPROGRAMSANDHOWTODROPTHEMFINALLY,YOUWILLALSOLEARNTODEFINEARGUMENTSFORPROGRAMSPROGRAMATTRIBUTESSCHEDULERPROGRAMSHAVEASPECIFICSETOFATTRIBUTESTHATYOUCANSETTODEFINETHECHARACTERISTICSOFTHEPROGRAMTHESEATTRIBUTESCANBESETATCREATIONTIMETHROUGHTHEFOLLOWINGCREATE_PROGRAMPROCEDUREPARAMETERSPROGRAM_NAMETHEPROGRAM_NAMEPARAMETERSPECIFIESTHENAMEASSIGNEDTOTHENEWPROGRAMBECAUSEPROGRAMSARESTOREDLIKEANYOTHERDATABASEOBJECT,STANDARDORACLEOBJECTNAMINGREQUIREMENTSAREENFORCEDFORPROGRAMSTHISMEANSTHATTHEPROGRAMNAMEMUSTNOTONLYBEAVALIDORACLEOBJECTNAME,ITMUSTALSOBEUNIQUEWITHINTHESCHEMAUSINGSCHEDULESSCHEDULESDEFINEWHENJOBSRUNASWELLASWHENWINDOWSAREOPENEDWINDOWSWILLBECOVEREDLATERINTHISCHAPTERLIKEJOBSANDPROGRAMS,SCHEDULESARESTOREDOBJECTSANDFOLLOWALLTHESAMENAMINGREQUIREMENTSBYSAVINGSCHEDULESASINDEPENDENTOBJECTS,THEYCANBEUSEDBYMULTIPLEJOBSSCHEDULESDEFINENOTONLYWHENAJOBWILLSTART,BUTALSOHOWOFTENTHEJOBWILLBEREPEATEDTHISISKNOWNASTHEREPEATINTERVALORACLESSCHEDULEROFFERSTWOWAYSTODEFINETHEINTERVALUSINGPL/SQLEXPRESSIONSORUSINGTHEPOWERFULNEWCALENDARINGSYNTAXINTRODUCEDINORACLE10GSCHEDULEATTRIBUTESSCHEDULEOBJECTSHAVEASPECIFICSETOFATTRIBUTESTHATYOUCANSETTODEFINETHECHARACTERISTICSOFTHESCHEDULETHESEATTRIBUTESCANBESETATCREATIONTIMETHROUGHTHEFOLLOWINGCREATE_SCHEDULEPROCEDUREPARAMETERSSCHEDULE_NAMETHESCHEDULE_NAMEPARAMETERSPECIFIESTHENAMEOFTHESCHEDULEBECAUSESCHEDULESARESTOREDLIKEANYOTHERDATABASEOBJECT,STANDARDORACLEOBJECTNAMINGREQUIREMENTSAREENFORCEDFORSCHEDULESTHISMEANSTHATTHEPROGRAMNAMEMUSTNOTONLYBEAVALIDORACLEOBJECTNAME,ITMUSTALSOBEUNIQUEWITHINTHESCHEMASTART_DATETHESTART_DATEPARAMETERSPECIFIESTHEFIRSTDATETHATTHESCHEDULEI