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SENIOR ORACLE DBA INTERVIEW QUESTIONS


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stion 1. Explain the i!e"en#e $et%een a hot $a#&up an a #ol $a#&up an the $ene'ts#iate %ith ea#h.

%e"(t backup is basically taking a backup of the database while it is still up and running and it must be inve log mode. A cold backup is taking a backup of the database while it is shut down and does notre being in archive log mode. The benefit of taking a hot backup is that the database is still availablese while the backup is occurring and you can recover the database to any point in time. The benefitking a cold backup is that it is typically easier to administer the backup and recovery process. Inion, since you are taking cold backups the database does not require being in archive log mode andthere will be a slight performance gain as the database is not cutting archive logs to disk.stion ). *ou ha+e ,ust ha to "esto"e -"o $a#&up an o not ha+e an/ #ont"ol 'les. 0o% /ou o a$out $"inin up this ata$ase2

%e"(uld create a text based backup control file, stipulating where on disk all the data files where and thene the recover command with the using backup control file clause.stion 3. 0o% o /ou s%it#h -"o an init.o"a 'le to a sp'le2%e"(e the create spfile from pfile command.stion 4. Explain the i!e"en#e $et%een a ata $lo#&5 an extent an a seent.%e"(ta block is the smallest unit of logical storage for a database object. As objects grow they takeks of additional storage that are composed of contiguous data blocks. These groupings of guous data blocks are called extents. All the extents that an object takes when grouped together areidered the segment of the database object.stion 6. 7i+e t%o exaples o- ho% /ou iht ete"ine the st"u#tu"e o- the ta$le DE8T.

%e"(the describe command or use the dbms!metadata.get!ddl package.stion 9. Whe"e %oul /ou loo& -o" e""o"s -"o the ata$ase enine2%e"(e alert log.


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stion :. Copa"e an #ont"ast TRUNCATE an DELETE -o" a ta$le.%e"(the truncate and delete command have the desired outcome of getting rid of all the rows in a table.

difference between the two is that the truncate command is a ##$ operation and just moves the highr mark and produces a no rollback. The delete command, on the other hand, is a #%$ operation,h will produce a rollback and thus take longer to complete.stion ;. 7i+e the "easonin $ehin usin an inex.%e"(er access to data blocks in a table.stion #"eate it. 0o% /ou o this %ithout a!e#tin the #hil"en ta$les2

%e"(ble the foreign key constraint to the parent, drop the table, re'create the table, and enable the foreignconstraint.

stion 13. Explain the i!e"en#e $et%een ARC0IVELO7 oe an NOARC0IVELO7e an the $ene'ts an isa+antaes to ea#h.

%e"(*I+$- mode is a mode that you can put the database in for creating a backup of all transactionshave occurred in the database so that you can recover to any point in time. /-A()*I+$- modesically the absence of A()*I+$- mode and has the disadvantage of not being able to recover topoint in time. /-A()*I+$- mode does have the advantage of not having to write transactions torchive log and thus increases the performance of the database slightly.stion 14. What #oan %oul /ou use to #"eate a $a#&up #ont"ol 'le2%e"(( #ATA"A0 "A)12 )-/T(-$&I$ T- T(A)


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stion 16. 7i+e the staes o- instan#e sta"tup to a usa$le state %he"e no"al use"s a/ a##ess

%e"(TA(T2 /-%-/T ' Instance startup$T( #ATA"A0 %-/T ' The database is mounted$T( #ATA"A0 -2/ ' The database is openedstion 19. What #olun i!e"entiates the V? +ie%s to the 7V? +ie%s an ho%2%e"(/0T!I# column which indicates the instance in a (A) environment the information came from.stion 1:. 0o% %oul /ou o a$out ene"atin an E@8LAIN plan2%e"(te a plan table with utlxplan.sql.

the explain plan set statement!id 3 4tst54 into plan!table for a 06$ statementat the explain plan with utlxplp.sql or utlxpls.sql

stion 1;. 0o% %oul /ou o a$out in#"easin the $u!e" #a#he hit "atio2%e"(the buffer cache advisory over a given workload and then query the v7db!cache!advice table. If age was necessary then I would use the alter system set db!cache!si8e command.stion 1=1666%e"(get this error when you get a snapshot too old within rollback. It can usually be solved by increasingndo retention or increasing the si8e of rollbacks. 9ou should also look at the logic involved in thecation getting the error message.stion )=. Explain the i!e"en#e $et%een ?ORACLE0OE an ?ORACLEBASE.%e"(

)$!"A0 is the root directory for oracle. -(A)$!*-% located beneath -(A)$!"A0 ise the oracle products reside.stion )1. 0o% %oul /ou ete"ine the tie one une" %hi#h a ata$ase %as ope"atin2%e"(ct #"TI%:-/ from dual;stion )). Explain the use o- settin 7LOBALNAES eual to TRUE.%e"(ng 7LOBALNAES dictates how you might connect to a database. This variable is either T( or 0 and if it is set to T( it enforces database links to have the same name as the remote databasehich they are linking.


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stion )3. What #oan %oul /ou use to en#"/pt a 8LSQL appli#ation2%e"(A2stion )4. Explain the i!e"en#e $et%een a FUNCTION5 8ROCEDURE an 8ACGA7E.%e"(ction and procedure are the same in that they are intended to be a collection of 2$=06$ code that

es a single task. Timed 0tatisticsstion ):. Whe"e in the O"a#le i"e#to"/ t"ee st"u#tu"e a"e auit t"a#es pla#e2%e"(ix 7-(A)$!*-%=rdbms=audit,ndows the event viewer stion );. Explain ate"ialie +ie%s an ho% the/ a"e use.%e"(riali8ed views are objects that are reduced sets of information that have been summari8ed, grouped,gregated from base tables. They are typically used in data warehouse or decision support systems.stion )


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of +7000I-/ and +7000I-/!


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( #ATA"A0 #ATA&I$ @datafile!name (0I: @new!si8e;stion 41. What +ie% %oul /ou use to loo& at the sie o- a ata 'le2%e"(!#ATA!&I$0stion 4). What +ie% %oul /ou use to ete"ine -"ee spa#e in a ta$lespa#e2%e"(!&(!02A)stion 43. 0o% %oul /ou ete"ine %ho has ae a "o% to a ta$le2%e"(on fine grain auditing for the table.stion 44. 0o% #an /ou "e$uil an inex2%e"(

( I/#B @index!name ("I$# -/$I/;stion 46. Explain 8a"titionin an $ene'ts o- usin 8a"tionin.%e"(tioning is a method of taking large tables and indexes and splitting them into smaller, moreageable pieces.stion 49. *ou ha+e ,ust #opile a 8LSQL pa#&ae $ut ot e""o"s5 ho% %oul /ou +ie% the"s2%e"(< ((-(0stion 4:. 0o% #an /ou athe" statisti#s on a ta$le2%e"(A/A$9: command or #"%0!0TAT package.stion 4;. 0o% #an /ou ena$le a t"a#e -o" a session2

%e"(the #"%0!000I-/.0T!06$!T(A) or se( 000I-/ 0T 06$!T(A) 3 T(;stion 4


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ws data to be loaded that has been produced by other utilities from different data sources just so longconforms to A0)II formatted or delimited files.stion 6=. Nae t%o 'les use -o" net%o"& #onne#tion to a ata$ase.%e"(/A%0.-(A and 06$/T.-(Astion 61. Explain i!e"en#e $et%een O"a#le Data$ase an Instan#e%e"(le database consist of followingD

#atafiles, )ontrol &iles, (edo $og &ilesle instance consist of followingD0A and -racle processes E#"ue"/2%e"(elated sub'query is a sub'query, which has reference to the main querystion 64. Whi#h one o- the $elo% #hane %ill e#"ease 8A7IN7SWA88IN7%e"(/)(A0 0-(T!A(A!(TAI/#!0I:DECREASE S0ARED8OOLSIE J#o""e#t ans%e"K#)(A0 -2/!)(0-(0 parameters/)(A0 #"!)A)*!0I:stion 66. Explain steps in+ol+e in i"ation -"o O"a#le


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stion 6:. Lo#all/ anae TE8 Ta$lespa#e is 1== FULL an the"e is no spa#e a+aila$le toata'le to in#"ease TE8 ta$lespa#e. What #an /ou o that iht -"ee up TE8 spa#e2

%e"(can try one of the following to free up T%2 spacessue A$TT( TA"$02A) 2)TI/)(A0 5 followed by

A$TT( TA"$02A) 2)TI/)(A0 J command;)lose some of the idle sessions connected to the databasestion 6;. List '+e ost ipo"tant -eatu"es o- O"a#le


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+%0TAT, 0A(, and 2(0TAT command to get more information on )2 andory usage and possible blocking0TAT02A)1 report to identifyDT-2 M


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A0)A#I/ 0TA/#"9 is a standby database that receives its (#- information from another /#"9 database Enot from 2rimary databaseF.stion 9:. What a"e soe o- the $a ta$les /ou ue"/ to 'n out a$out UNDO seents2%e"(would queryD#"A!/#-!00

+7/#-0TATstion 9;. What oes Blo#& eia Re#o+e"/ JBRK o2%e"(

is responsible for restore and recover of specified "$-)1stion 9


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h 8a"titionin sed to spread data evenly over partitions. 2ossible usageD data has no logicalpings.8a"titionin sed to list together unrelated data into partitions. 2ossible usageD a number of statesartitioned into a region.posite Rane>0ash 2artitioning sed to range partition first, then spreads data into hash partitions.ible usageD range partition by date of birth then hash partition by name; store the results into thepartitions.posite Rane>List 2artitioning sed to range partition first, then spreads data into list partitions.ible usageD range partition by date of birth then list partition by state, then store the results into theartitions.stion :6. 0o% to #on+e"t a Sinle Instan#e


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oved throughputability over single instance systemsoved response timeavailabilitysparencystion ::. Explain Ro% Lo#&in an ulti>+e"sion Rea Consisten#/ in RAC

%e"(le4s row locking feature allows multiple transactions from separate nodes to lock and updateent rows of the same data block. This is done without any of the transactions waiting for the othersmmit. If a row has been modified but not yet committed, then the original row values are available tostances for read access. This is called multi'version read consistency.stion :;. What is an Exte"nal ta$le int"ou#e in


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ement failure failed 06$ is automatically rolled back and an error is returned to user.2rocess failure abnormal disconnect 2%-/ detects and rolls back and releases.rror Edrop table, dataF #"A is required to recover data Eimport or incomplete

veryFa &ailure $oss or corruption of files #"A needs to apply appropriate recovery.

nce &ailure Abnormal shutdown Instance simply needs restarted, 0%-/ autovers byD(olling forward changes in the redo log not recorded in the data files before -pen of database.(ollbacks can occur after the database is open, when block data is requested.stion ;). What oes RESETLO7S option o2%e"(eates a new incarnation of the database, putting a new 0)/ in all data file headers.

eset $og 0equence number to 5eformats -/$I/ (#- $-&I$0 if they existsstion ;3. Nae 6 s/ste +ie%s that #an $e use to "et"ie+e in-o"ation a$out $a#&up an+e"/

%e"(

A)12ATA&I$!*A#()-+(!&I$)-+(9!$-)-+(9!0TAT0stion ;4. What is the ui#&est %a/ to #lone a ata$ase i+e /ou" $a#&up is one +ia RAN2%e"(g (%A/ command #2$I)AT #ATA"A0

stion ;6. What is the use o- the RESUABLE pa"aete" in E@8ORT2%e"((0%A"$ parameter allows the export to. 0uspend if a space allocation issue occurs.


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stion ;:. Nae 6 init.o"a pa"aete"s that nees to set in 8"ia"/ ata$ase -o" Data7ua"'u"ation%e"(5......!A()*I+!#0T!K!A()*I+!#0T!K!0TAT!)$I/T

!0(+(/#"9!A()*I+!#0T/#"9!&I$!%A/A%/Tstion ;;. What is the use o- FORCE LO77IN7 option2%e"(etting &-() $-I/ to T(, all transactions will generate (#-. This is used for #ata uard,o data will be missed Ei.e. transactions that were run with /-$-I/ optionF in 0tandby database.stion ;


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%e"( the processing of the remote data to the remote instance by using a view to pre'select the

mation for the join. This will result in only the data required for the join being sent across.stion


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%e"(ge number of small shrinks indicates a need to increase the si8e of the rollback segment extents.ly you should have no shrinks or a small number of large shrinks. To fix this just increase the si8e of xtents and adjust optimal accordingly.stion 1=1. *ou loo& at the $a"oll$a#&ses +ie% an see that /ou ha+e a la"e nu$e" o- ps is this a p"o$le2%e"(ge number of wraps indicates that your extent si8e for your rollback segments are probably too small.ase the si8e of your extents to reduce the number of wraps. 9ou can look at the average transactionn the same view to get the information on transaction si8e.stion 1=). 0o% an/ "eo los shoul /ou ha+e an ho% shoul the/ $e #on'u"e -o"iu "e#o+e"a$ilit/2

%e"(should have at least three groups of two redo logs with the two logs each on a separate disk spindleored by -racleF. The redo logs should not be on raw devices on /IB if it can be avoided.stion 1=3. I- the ata$ase #annot $e $oun#e5 ho% %oul /ou &ill a use"2%e"(commandDA$T( 090T% 1I$$ 000I-/ 0I#,0(IA$W ;stion 1=4( What is the -"euen#/ o- lo Upate..2%e"(ommit or heckpoint or olog buffer is 5=Grd fullstion 1=6( 0o% o /ou "enae a ata$ase2

%e"(can change #atabase name by following below procedureDer #atabase backup control file to trace;

bove step will create a text control file in user!dump!dest directory.hange name of the #atabase in above file and in init.ora file.TA(T2 /-%-/Tun the script that was modified in step GT( #ATA"A0 -2/ (0T$-0;stion 1=9( Is it possi$le to #on'u"e p"ia"/ se"+e" an stan $/ se"+e" on i!e"ent OS2%e"(wer for this questions is /-. 0tandby database must be on same version of database and sameon of -perating system.


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stion 1=:( What oes ata$ase o u"in ountin p"o#ess2%e"( mounting the database oracle reads the data from controlfile which is used for verifying physical

base files during sanity check. "ackground processes are started before mounting the database only.stion 1=;( What is a ealo#& an Explain%e"(adlock is a condition where two or more users are waiting for data locked by each other. -raclematically detects a deadlock and resolves them by rolling back one of the statements involved in thelock, thus releasing one set of data locked by that statement. 0tatement rolled back is usually thewhich detects the deadlock. #eadlocks are mostly caused by explicit locking because oracle doeso lock escalation and does not use read locks. %ulti'table deadlocks can be avoided by locking thes in same order in all the applications, thus precluding a deadlock.

stion 1=


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e are main two causes for reparsingDe objects which the query is referencing has been modifiede parsed version of sql text has been aged out of the library cache.stion 114( 0o% to ipleent the ultiple #ont"ol 'les -o" an existin ata$ase%e"(it init.ora file, set control!files parameter with multiple locationutdown immediatepy control file to multiple locations > confirm from init.ora contol!files parameter art the database.n this query for changes confirmation ' select name from v7controlfile;stion 116( What is ean $/ 8"o"a 7lo$al A"ea J87AK%e"(

' 2rogram lobal Areae 2rocess lobal Area is a memory region that contains data and control information for a singleer process or a single background process.2A is allocated when a process is created and de'allocated when the process is terminated. 2A isrea that is used by only one process.stion 119( What is eant $/ "e#u"si+e hints2%e"(ber of times processes repeatedly query the dictionary table is called recursive hints. It is due toata dictionary cache is too small. "y increasing the 0*A(#!2--$!0I: parameter we can

mi8e the si8e of #ata #ictionary )ache.stion 11:( Is it possi$le to use "a% e+i#es as ata 'les an %hat is the a+antaes o+e"/ste 'les 2%e"(

advantages over file system filesDwill be improved because -racle will bypass the -0. #isk )orruption will be very less.stion 11;( What a"e isa+antaes o- ha+in "a% e+i#es2%e"(have to depend on export=import utility for backup=recoveryar command cannot be used for physical file backup, instead we have to use dd command which isflexible and has limited recoveries.stion 11


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stion 1)=. Explain i!e"ent le+el o- Auitin%e"(ement Auditingege Auditingct Auditingstion 1)1. Explain the i!e"en#e $et%een ?ORACLE0OE an ?ORACLEBASE.%e"()$!"A0 is the root directory for oracle. -(A)$!*-% located beneath -(A)$!"A0 ise the oracle products reside.stion 1)). Nae th"ee a+iso"/ statisti#s /ou #an #olle#t.%e"(base )ache Advisory

ed 2ool AdvisoryAdvisorystion 1)3. When a use" p"o#ess -ails5 %hat $a#&"oun p"o#ess #leans up a-te" it2%e"(/stion 1)4. 0o% %oul /ou -o"#e a lo s%it#h2%e"(( 090T% 0


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stion 1)


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stion 14). 0o% o /ou put ata$ase is ARC0IVELO7 oe5 explain p"o#eu"e%e"(odify init.ora parameter 0TA(T!A()*I+3T(6$ 0*T#-


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stion 14


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%e"(pical +)0 configuration, there are three main resources required for -racle database failover.acle #atabase

stener esystemsstion 166. Whi#h 'le #ontains VCS se"+i#e "oup an "esou"#e in-o"ation2%e"(.cf stion 169. What ata$ase "elate in-o"ation %e nee to set in VCS2%e"()$!0I#/( name

/( password Eif usedFle filesystems that will be failed over tion to init.ora=spfile if not available at default locationstion 16:. What is VCS in>epth onito"in2%e"()0 in'depth monitoring, a database user E+)0%-/F will be created which will login to database atin interval Ei.e. every M minuteF to see if database connectivity is -1. &or some reason, if this user login +)0 will fail over the database to second node.

stion 16;. In ACTIVE VCS en+i"onent5 /ou nee to "e#/#le the ata$ase $ut oesnt %ant$ase to -ailo+e" to othe" noe.


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stion 191. 0o% o /ou REBUILD inex online an Copute Statisti#s at the sae tie2%e"(( I/#B I/#B!/A% REBUILD )-%2T 0TATI0TI)0 ONLINEstion 19). Explain Bitap Poin Inexes%e"(ap ?oin Indexes pre'stores results of a join and can avoid an expensive join operation at runtime.stion 19). Whi#h pa"aete"s #an $e oi'e /nai#all/ as pa"t o-


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%e"(base $atchesDo Allocation $atcho )opy $atch)ache $atch+7$AT)*, +7$AT)**-$#(, +7$AT)*/A% to get more information about the latchesstion 196. In %hi#h s#ena"ios /ou nee to set La"e 8ool2%e"(need to set $arge 2ool if you are using belowDE%ultithreaded 0erverF/ backupsstion 199. Explain Tunin 8"o#ess that in+ol+es Appli#ation5 Data$ase5 OS5 Net%o"&

%e"(ch a scenario, tuning should perform in following orderD"usiness (ules#ata #esignApplication #esign$ogical 0tructure of the #atabase#atabase -perationsAccess 2ath%emory AllocationI=- and 2hysical 0tructure of the #atabase(esource Allocation. -0stion 19:. Explain Di!e"ent Tunin A"eas in Data$ase

%e"(wing areas within database can be tunedDory '

ce %anagemento > )heckpointack 'ed 2ool, "uffer )ache, (edo "uffer, 0ort Area 0i8e, 2A, $arge 2oolple #atabase


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stion 1:=. 0o% #an /ou setup En#"/ption in Data$ase2%e"(within #atabase can be encrypted and decrypted using packageD0!-"&0)ATI-/!T--$1ITstion 1:1. Nae '+e pa"aete"s #an $e use -o" 8ass%o" anaeent2%e"(wing parameters can be used to manage user passwordD

#!$-I/!ATT%2T00


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hni#al UNI@y #"A should know something about the operating system that the database will be running on. Thetions here are related to /IB but you should equally be able to answer questions related tomon


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stion


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stion 1:. What is Seapho"e2%e"(ta object that represents the right to use a limited resource, used for synchroni8ation andmunication between asynchronous processes.stion 1;. 0o% o /ou exe#ute a UNI@ #oan in the $a#&"oun2%e"(can use > at the end of command or use nohup commandstion 1


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CTICAL ORACLE DBA QUESTIONS("A interview can be difficult both for the interviewer and the candidate. The role involves technical, process skills, and personal communications skills. Although those three skill sets are all critical,Y#"A interview questionsY articles in the past have focused only on the questions you can use to

e a person s technical qualifications. In this article, you will see questions an interviewer can pose to#"A candidate to judge the other attributes of the job.dition, this article includes a set of questions #"As should ask at some point during their interviews.interviewer stops and asks Y#o you have any questions for meXY don t sit there quietly. The

hasis of the #"A questions provided in this article is the organi8ation s process focus and itsnical career path for #"As. All of the questions provided here are intended as starting points; basede answers to the questions, you should ask follow'ups to understand how the answer will affect your o'day activities and your long'term prospects. -f course, if you ask a question to the interviewer, you

ld be prepared to answer the same question concerning your present work environment.stions to as& the inte"+ie%e"(ess #ont"ol issues(t processes do you follow while implementing changes in productionXde the #"As and system administrators, who has access to the Y-racleY operating system accountXoften is the oracle operating system account password changedXhe #"As co'located with the teams they supportX *ow is capacity planning performedXere adequate capacity already in place to support the expected growth over the next yearX &uturertunities=organi8ation issuesD

ere a formal job definition for the #"A roleX Is there a defined technical career pathXis IT aligned with the business areasXmany employees report to more than one managerX *ow do you determine if a #"A has beenessfulX

are the application #"As and production control #"As organi8edXstions that %ill $e as&e to /oun s&ills(

se bring along a copy of the last status report you ve submitted, as well as any articles. If you haven tght one along, please mail me one after the interview.e+e"an#e in te#hni#al expe"tise(t errors did you hit during your most recent database recoveryXt was the most difficult technical obstacle you encountered during your last projectXe+e"an#e in "elationships(t negative Ygroup relationshipY issues exist in your current working environmentX *ow are youessing themXt is your most difficult set of users, and how do you manage that relationshipX


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e are samples; use a question from each category to guide a discussion of the way themunications skills, process knowledge, and technical aspects of the job are interrelated in the role. If nterviewer and the candidate can agree on what a successful #"A looks like in the environment, is a strong foundation for a future working relationship.

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