d2k Interview Questions

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Important Questions in Oracle, Developer /2000(Form 4.5 and Reports 2.5)

Oracle

1) What are the Back ground processes in Oracle and what are they.1) This is one of the most frequently asked question.There are basically 9 rocesses but in a general systemwe need to mention the first fi!e background processes.They do the house keeping acti!ities for the Oracle and

are common in any system.The !arious background processes in oracle area) Data ase !riter(D!R) "" #ata Base Writer Writes $odified blocks from #atabase buffer cacheto #ata %iles.This is required since the data is not written whene!er a transaction is commited.

b)"o#!riter("$!R) %% &ogWriter writes the redo log entries to disk. 'edo &og data is generated inredo log buffer of (*. *s transaction commits and log buffer fills+ &W' writes log entries into aonline redo log file.

c) &'stem onitor(&O) %%The (ystem $onitor performs instance reco!ery at instance startup.Thisis useful for reco!ery from system failure

d)*rocess onitor(*O) %%The rocess $onitor peforms process reco!ery when user rocess fails.mon ,lears and %rees resources that process was using.

e) +ec-*oint(+*) %%*t (pecified times+ all modified database buffers in (* are written to datafiles by #BW' at ,heckpoints and -pdating all data files and control files of database to indicate themost recent checkpoint

f)rcieves(R+1) %%The *rchi!er copies online redo log files to archi!al storal when they are busy.

g) Recoveror(R+O) %%The 'eco!eror is used to resol!e the distributed transaction in network

h) Dispatcer (Dnnn) %%The #ispatcher is useful in $ulti Threaded *rchitecturei) "c-n %%We can ha!e upto 1 lock processes for inter instance locking in parallel sql.

/) 0ow many types of (ql (tatements are there in Oracle/) There are 3asicall' t'pes o s6l statments.They area) Data Deination "an#ua#e(DD") "" The ##& statments define and maintain obects and drop obects.b) Data anipulation "an#ua#e(D") "" The #$& statments manipulate database data.c) ransaction +ontrol &tatements "" $anage change by #$&d) &ession +ontrol "" -sed to control the properties of current session enabling anddisabling roles and changing .e.g "" *lter (tatements+(et 'olee) &'stem +ontrol &tatements "" ,hange roperties of Oracle 2nstance .e.g"" *lter (ystemf) m3edded &6l "" 2ncorporate ##&+#$& and T.,.( in rogramming &anguage.e.g""-sing the (ql (tatements in languages such as 3,3+ Open+%etch+ e4ecute and close

5) What is a Transaction in Oracle5) * transaction is a &ogical unit of work that compromises one or more (6& (tatements e4ecuted by a single-ser. *ccording to *7(2+ a transaction begins with first e4ecutable statment and ends when it is e4plicitly

commited or rolled back.

4) e' !ords 7sed in Oracle8) The ey words that are used in Oracle are ""a) +ommitin# %" * transaction is said to be commited when the transaction makes permanent changesresulting from the (6& statements.b) Roll3ac- "" * transaction that retracts any of the changes resulting from (6& statements inTransaction.c) &ave*oint "" %or long transactions that contain many (6& statements+ intermediate markers orsa!epoints are declared. (a!epoints can be used to di!ide a transactino into smaller points.d) Rollin# For8ard %%rocess of applying redo log during reco!ery is called rolling forward.e) +ursor %%* cursor is a handle : name or a pointer) for the memory associated with a specific

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stament. * cursor is basically an area allocated by Oracle for e4ecuting the (ql (tatement. Oracle uses animplicit cursor statement for (ingle row query and -ses ;4plcit cursor for a multi row query.f) &'stem $lo3al rea(&$) "" The (* is a shared memory region allocated by the Oracle that contains#ata and control information for one Oracle 2nstance.2t consists of #atabase Buffer ,ache and 'edo log Buffer.g) *ro#ram $lo3al rea (*$) %" The * is a memory buffer that contains data and control information forser!er process.g) Data3ase uer +ace %" #atabese Buffer of (* stores the most recently used blocks of datatbasedata.The set of database buffers in an instance is called #atabase Buffer ,ache.h) Redo lo# uer%% 'edo log Buffer of (* stores all the redo log entries.i) Redo "o# Files%%'edo log files are set of files that protect altered database data in memory that has notbeen written to #ata %iles. They are basically used for backup when a database crashes.

) *rocess%" * rocess is a 3thread of control3 or mechansim in Operating (ystem that e4ecutes series of steps.

arious Optimisation techniques are

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a) :ecute *lan %%we can see the plan of the query and change it accordingly based on the inde4es3) Optimi;er


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b) (hare lockWe can do the table as (hareC&ock as many shareClocks can be put on the same resource.

/1) re!ileges and rants/1) re!ileges are the right to e4ecute a particulare type of (6& statements.e.g "" 'ight to ,onnect+ 'ight to create+ 'ight to resourcerants are gi!en to the obects so that the obect might be accessed accordingly.The grant has to begi!en by the owner of the obect.

//)Table (pace+#ata %iles+arameter %ile+ ,ontrol %iles//)Table (pace "" The table space is useful for storing the data in the database.When a database is createdtwo table spaces are created.a) (ystem Table space "" This data file stores all the tables related to the system and dba tablesb) -ser Table space "" This data file stores all the user related tablesWe should ha!e seperate table spaces for storing the tables and inde4es so that the access is fast.#ata %iles "" ;!ery Oracle #ata Base has one or more physical data files.They store the data for thedatabase.;!ery datafile is associated with only one database.Once the #ata file is created the siHe cannotchange.To increase the siHe of the database to store more data we ha!e to add data file.arameter %iles "" arameter file is needed to start an instance.* parameter file contains the list of instanceconfiguration parameters e.g.""dbCblockCbuffers I


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/9) ,odd 'ules describe the ideal nature of a '#B$(. 7o '#B$( satisfies all the 1/ codd rules and Oracle(atisfies 11 of the 1/ rules and is the only 'dbms to satisfy the ma4imum number of rules.

5) What is 7ormalisation5) 7ormalisation is the process of organising the tables to remo!e the redundancy.There are mainly ;C#*T;(K(T;$.(-';((CWO'27

5) What are obect groupJ*n obect group is a container for a group of obects. Kou define an obect group when you want to package relatedobects so you can copy or reference them in another module.

8) What are referenced obectsJ'eferencing allows you to create obects that inherit their functionality and appearance from other obects.'eferencing an obect is similar to copying an obect+ e4cept that the resulting reference obect maintains a link to itssource obect. * reference obect automatically inherits any changes that ha!e been made to the source obect whenyou open or regenerate the module that contains the reference obect.


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e.g "" eyNne4tNfield+ eyNup+eyN#ownouse ri##ers %%$ouse Triggers are fired as a result of the mouse na!igation.e.g. WhenNmouseNbuttonNpressed+ whenNmouseNdoubleclicked+etcavi#ational ri##ers %%These Triggers are fired as a result of 7a!igation.;.g " ostNTe4tNitem+reNte4tNitem.We also ha!e e!ent triggers like when newNformNinstance and whenNnewNblockNinstance.We cannot call restricted procedures like goCto:PmyCblock.firstCitemQ) in the 7a!igational triggersBut can use them in the eyNne4tNitem.e Dierence 3et8een e'Ane:t and *ostAe:t is an ver' important 6uestion.The keyNne4t is fired as a result of the key action while the post te4t is fired as a result of the mouse mo!ement. eyne4t will not fire unless there is a key e!ent.The sequence of firing in a te4t item are as follows "" a) pre N te4t b) when new item

c) keyNne4t d) when !alidate

e) post te4t

1 ) ,an you store pictures in databaseJ 0owJ1)Kes + in long 'aw datatype.

11) What are property classes J ,an property classes ha!e triggerJ

11) roperty class inheritance is a powerful feature that allows you to quickly define obects that conform to your owinterface and functionality standards. roperty classes also allow you to make global changes to applications quicklyBy simply changing the definition of a property class+ you can change the definition of all obects that inherit propertfrom that class.Kes . *ll type of triggers .

1/ a) 2f you ha!e property class attached to an item and you ha!e same trigger written for the item . Which will fire firstJItem level tri##er ires , 2f item le!el trigger fires+ property le!el trigger won3t fire. Triggers at the lowest le!el arealways gi!en the first preference. e item level tri##er ires irst and ten te 3loc- and ten te Form leveltri##er.15) What are record groups J @ ,an record groups created at runNtimeJ record #roup is an internal Oracle Forms data structure tat as a column/ro8 rame8or- similar to adata3ase ta3le. 0owe!er+ unlike database tables+ record groups are separate obects that belong to the form moduin which they are defined. * record group can ha!e an unlimited number of columns of type ,0*'+ &O7+ 7-$B;or #*T; pro!ided that the total number of columns does not e4ceed ?8. 'ecord group column names cannot e4ce5 characters.rogrammatically+ record groups can be used whene!er the functionality offered by a twoNdimensionaarray of multiple data types is desirable.C*& OF R+ORD $RO7*%Quer' Record $roup%* query record group is a record group that has an associated (;&;,T statement.The columns in a query record group deri!e their default names+ data types+ and lengths from the database columnsreferenced in the (;&;,T statement. The records in a query record group are the rows retrie!ed by the queryassociated with that record group.

onA6uer' Record $roup" * nonNquery record group is a group that does not ha!e an associated query+ but whosestructure and !alues can be modified programmatically at runtime.

&tatic Record $roup % * static record group is not associated with a queryE rather+ you define itsstructure and row !alues at design time+ and they remain fi4ed at runtime.

18) What are *&;'TJ18)*n *&;'T is a modal window that displays a message notifiying operator of some application

condition.

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item when the operator acti!ates the item with the mouse.

When $ouse 7a!igate is set to %alse+ Oracle %orms does not perform na!igation :and the resulting !alidation) to moto the item when an operator acti!ates the item with the mouse.

1A) What is %O'$(C$#2CW27#OWJ%orms run inside the $#2 application window. This property is useful for calling a form from another one.

1) What are timers J when whenNtimerNe4pired does not fireJThe WhenNTimerN;4pired trigger can not fire during trigger+ na!igation+ or transaction processing.

19 ) ,an obect group ha!e a blockJ19)Kes + obect group can ha!e block as well as program units.

/) 0ow many types of can!ases are there./)There are 2 t'pes o canvases called as +ontent and &tac- +anvas.+ontent canvas is te deault and the that is used mostly for gi!ing the base effect. 2ts like a plate on which we add items and stac-ed canvas is used o#ivin# dimensional eect.The following questions might not be asked in an *!erage 2nter!iew and could be asked when the 2nter!iewerwants to trouble u and go deepppppppppppppRR0e cannot go furtherR..

1) What are userNe4itsJ1) 2t in!okes 5& programs.

/) ,an you pass !alues toNandNfro from foreign function J how J/) Kes . Kou obtain a return !alue from a foreign function by assigning the return !alue to an Oracle %orms!ariable or item. $ake sure that the Oracle %orms !ariable or item is the same data type as the return !aluefrom the foreign function.

*fter assigning an Oracle %orms !ariable or item !alue to a &=(6& !ariable+ pass the &=(6& !ariable asa parameter !alue in the &=(6& interface of the foreign function. The &=(6& !ariable that is passed asa parameter must be a !alid &=(6& data typeE it must also be the appropriate parameter type as definedin the &=(6& interface.

5) What is 2*LTB structure J5) The entries of ro @ , and user e4its and the form which simulate the proc or userCe4it are stored in 2*LTB tabin d=b.

8) ,an you call W27N(# thruo3 user e4itsJ8) K;(.


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application that will run against 7O7NO'*,&; datasources .ey setting unique :default.)

dateablenNupdateable.

&ocking mode "(pecifies when Oracle %orms should attempt to obtain database locks on rows that correspond to queried records in form.a) immediate b) delayed

11) What are sa!epoint mode and cursor mode properties J le!elJ11) (pecifies whether Oracle %orms should issue sa!epoints during a session. This property is included primarily foapplications that will run against nonNO'*,&; data sources. %or applications that will run against O'*,&;+ use thedefault setting.,ursor mode N define cursur state across transactionOpen=close.

1/) ,an you replace default form processing J 0ow J

15) What is transactional trigger propertyJ15) 2dentifies a block as transactional control block. i.e. non N database block that oracle forms should manage astransactional block.:7O7NO'*,&; datasource) default N %*&(;.

18) What is O&; automation J18) O&; automation allows an O&; ser!er application to e4pose a set of commands and functions that can bein!oked from an O&; container application. O&; automation pro!ides a way for an O&; container application to usthe features of an O&; ser!er application to manipulate an O&; obect from the O&; container en!ironment.:%O'$(CO&;)

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1) ,an u port applictions across the platformsJ howJ1) Kes we can port applications across platforms.,onsider the form de!eloped in a windows system.The form wouldbe generated in uni4 system by using f8isual attributes are the font+ color+ and pattern properties that you set for form and menu obects that appear in y

application3s interface.

/) #iff. between >*T and roperty ,lassJ imp/)7amed !isual attributes define only font+ color+ and pattern attributesE property classes can contain these and anyother properties.Kou can change the appearance of obects at runtime by changing the named !isual attributeprogrammaticallyE property class assignment cannot be changed programmatically.When an obect is inheriting from both a property class and a named !isual attribute+ the named !isualattribute settings take precedence+ and any !isual attribute properties in the class are ignored.

5 ) Which trigger related to mouseJ5) WhenN$ouseN,lick WhenN$ouseN#ouble,lick WhenN$ouseN#own

WhenN$ouseN;nter WhenN$ouseN&ea!e WhenN$ouseN$o!e WhenN$ouseN-p

8) What is ,urrent record attribute propertyJ8) (pecifies the named !isual attribute used when an item is part of the current record.,urrent 'ecord *ttribute is frequently used at the block le!el to display the current row in a multiNrecord2f you define an itemNle!el ,urrent 'ecord *ttribute+ you can display a preNdetermined item in a special color when itpart of the current record+ but you cannot dynamically highlight the current item+ as the input focus changes.

*T at run timeJ


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/) ,an u ha!e more than one layout in report/) 2t is possible to ha!e more than one layout in a report by using the additional layout option in the layout

editor.

5) ,an u run the report with out a parameter form5) Kes it is possible to run the report without parameter form by setting the *'*$ !alue to 7ull

8) What is the lock option in reports layout8) By using the lock option we cannot mo!e the fields in the layout editor outside the frame. This is useful for

maintaining the fields .

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