Oracle Support全球解答的最hot的21个成果

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RDBMS SUPPORT's TOP 21

   Oracle Worldwide Technical Support answers approximately 6000 questions
a week.  In the RDBMS support group we find there is often a common theme to
the questions. Following are some of the most commonly asked questions and
problems encountered in the RDBMS technical support group. These questions
are based on problems encountered by relatively new DBA's.  Also included
are answers and/or tools to help further identify the problem.

1.  Q. What should I do about this warning: "Warning in SQLPLUS "product
       information table not loaded"?
    A. Run ORACLEHOME/sqlplus/admin/pupbld.sqlassystem(seeappendixofsqlplusreferenceguidefordetails).2.Q.HowcanusersberestrictedfromissuingDMLfromSQLPLUS(whenwithinformstheyarerestrictedbutinSQLPLUStheyarent)A.UsetheProductUserProfiletableinSQLPLUS(createdbypupbld.sql.)3.Q.Tryingtorestorefromafullexportandgetting"duplicatekeyinindex".Whyisthisoccurring?A.TheDBwasnotreinitializedbeforeimportrecreateDB,runcatalog.sqlandexpvew.sql.4.Q.Whyisperformanceslowonanparticularapplication?A.RunEXPLAINPLANandTkproftogatherinfoaboutexecutionplanandsomestatistics(thisdoesntnecessarilysolvetheproblembutwillhelptoidentifyit).5.Q.WhyisatablespacethathasbeendroppedstillintheDataDictionary?A.ItisprobablyintheDDasinvalid...itwillremainthereunlesstheDBisreinitialized.6.Q.Icantcreateobjectsinnewtablespaces.Whatswrong?A.LookinDBAROLLBACKSEGStobesurethereare2rollbacksegments.Ifthereisntcreateanother(restartDBwithitaddedtoinit.oraifitisprivate)beforecreatingobjects.7.Q.Whyistheprivaterollbacksegmentthatwasjustcreatednotbeingused?A.Ifitisprivateitmustbeaddedtoinit.oraandtheDBrestartedbeforeitwillbeacquired.8.Q.WhatdoIdowhenanapplicationishanging?A.UseSQLDBAMonitorLocks(alsotablesandprocesses)todetermineifthetable(orrow)islockedandreviewtracefilesandalert.logforerrors(thisdoesntnecessarilysolvetheproblembutwillhelptoidentifyit).9.Q.HowcanyoushrinkaRollbackSegment??(Orthevariation:arentRollbackSegmentsdeallocated?)A.InV6rollbacksegmentsarentdeallocatedandyoumustdropandrecreateto"shrink"them...inV7youcanspecifyan"OPTIMALSIZE"thattherollbacksegmentwillshrinkto.10.Q.Howdoyoumovedatafromonetablespacetoanother?A.Seepage33oftheV6UtilitiesGuide(youneedtorevoke,grant,alteruser,imp)11.Q.WhyisacreatedPublicRollbackSegmentnotusedbytheapplication?A.Iftransactions/transactionsperrollbacksegmentislessthanonethanonlyonerollbacksegmentwillbeacquiredanditwillbesystem.MaketherationofthetwobeequaltothenumberofRollbackSegments.12.Q.Thedatabaseishanging,userscanlogon,butnotdoanywork.WhatcanIdo?A.Checkwhetherthearchiverisstuck(alert.logwouldshowORA255).Eithermakespaceinthearchivaldestination,orchangethelogarchivedestparameter.13.Q.HowcanIgetafullerrorlisting?A.Addtracingtoyoursessionbyissuinganaltersessionsetsqltracetrue.LookfortracefilesintheUSERDUMPDESTdirectory.14.Q.Iremovedthedatafilebeforedroppingthetablespace.HowcanIrecoverfromthis?A.1)shutdown2)startupmount3)alterdatabasedatafilefullpathofremovedDFofflinedrop4)alterdatabaseopen5)droptablespacetsnameincludingcontents15.Q.IhaveDBAprivilegesandstillcantconnectinternal.Why?A.connectinternalischeckedattheOSlevel.InUnixitmeansthatyouruseridneedstobelistedattheDBAgroupinthe/etc/groupfile.16.Q.HowcanIcreateacopyofmydatabase?A.Doafullexportofthedatabase,precreatetheseconddatabaseincludingtheneededtablespace,thenperformfullimport.17.Q.Whyaresometablesmissingfromafullexport?A.ObjectsownedbySYSarenotexported.Youshouldntbecreatingtablesassys.18.Q.WhyisCharactertypeconversion3to1notsupportedonanimport?A.Thatsimporttellingyouitstryingtoloadavarcharintoachar.Youneedtogetav6exportofthev7databasebyusingthev6exportutilityagainstthev7database:1)runcatexp6.sqlassysonthev7database(thiswillestablishtheviewsneededforav6export.2)Fromthev6,setupTWOTASKtopointtothev7database,thenperformtheexport.19.Q.WhatdoIdoifDroptablespaceishanginginv6?A.MakesurethattheDCparametersarehighenough.dcfreeextents>selectcount()fromsys.fet;
       dc_used_extents > select count(*) from sys.uet$;
       row_cache_enqueue >= dc_free_extents dc_used_extents;

20. Q. How many blocks are actually used by the data in my tables ?
    A. This query will count all the blocks occupied by the table's data:
         select count(distinct(substr(ROWID, 1, 8) ||
                              (substr(ROWID, 15, 4))
             from

21. Q. How can I find all the duplicate entries in a table ?
       A. select * from real_table_name X
             where rowid < (select max(ROWID) from real_table_name where col1=X.col1 and col2=X.col2 .....) ;




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