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Oracle Aptitude Questions and Answers - 28 Nov 2008

Posted on :27-02-2016
Oracle Interview Questions and Answers - 28 Nov 2008:-

Q1. Which system variables can be set by users?

ANS:
SYSTEM.MESSAGE_LEVEL
SYSTEM.DATE_THRESHOLD
SYSTEM.EFFECTIVE_DATE
SYSTEM.SUPPRESS_WORKING.


Q2. What is ALERT?

ANS:
An ALERT is a modal window that displays a message notifying operator of some application condition.


Q3. What is call form stack?

ANS:
When successive forms are loaded via the CALL_FORM procedure, the resulting module hierarchy is known as the call form stack.


Q4. What is a visual attribute?

ANS:
Visual attributes are the font, color, and pattern properties that you set for form and menu objects that appear in your applications interface.


Q5. Which trigger related to mouse?

ANS:
When-Mouse-Click
When-Mouse-DoubleClick
When-Mouse-Down
When-Mouse-Enter
When-Mouse-Leave
When-Mouse-Move
When-Mouse-Up


Q6. Can you change VAT at run time?

ANS:
Yes. You can programmatically change an object named visual attribute setting to change the font, color, and pattern of the object at runtime.


Q7. What are the steps involved in Database Startup?

ANS:
Start an instance, Mount the Database and Open the Database.


Q8. What are the different modes of mounting a Database with the Parallel Server?

ANS:
Exclusive Mode: If the first instance that mounts a database does so in exclusive mode, only that Instance can mount the database.
Parallel Mode: If the first instance that mounts


Q9. What are the steps involved in Instance Recovery?

ANS:
Rolling forward to recover data that has not been recorded in data files, yet has been recorded in the on-line redo log, including the contents of rollback segments. Rolling back transactions that have been explicitly rolled back or have not been committed as indicated by the rollback segments regenerated in step a. Releasing any resources (locks) held by transactions in process at the time of the failure. Resolving any pending distributed transactions undergoing a two-phase commit at the time of the instance failure.


Q10. What are different modes of parameters used in functions and procedures?

ANS:
-IN
-OUT
-INOUT


Q11. Difference between procedure and function.

ANS:
Functions are named PL/SQL blocks that return a value and can be called with arguments procedure a named block that can be called with parameter. A procedure all is a PL/SQL statement by itself, while a Function call is called as part of an expression.


Q12. There is a string 120000 12 0 .125, how you will find the position of the decimal place?

ANS:
INSTR (120000 12 0 .125,1,.)
output 13


Q13. What is syntax for dropping a procedure and a function? Are these operations possible?

ANS:
Drop Procedure procedure_name
Drop Function function_name


Q14. What is a cursor for loop?

ANS:
Cursor For Loop is a loop where oracle implicitly declares a loop variable, the loop index that of the same record type as the cursors record.


Q15. How you were passing cursor variables in PL/SQL 2.2?

ANS:
In PL/SQL 2.2 cursor variables cannot be declared in a package. This is because the storage for a cursor variable has to be allocated using Pro*C or OCI with version 2.2, the only means of passing a cursor variable to a PL/SQL block is via bind variable or a procedure parameter.


Q16. Which is more faster - IN or EXISTS?

ANS:
EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.


Q17. When do you use WHERE clause and when do you use HAVING clause?

ANS:
HAVING clause is used when you want to specify a condition for a group function and it is written after GROUP BY clause. The WHERE clause is used when you want to specify a condition for columns, single row functions except group functions and it is written before GROUP BY clause if it is used.


Q18. What is difference between UNIQUE and PRIMARY KEY constraints?

ANS:
A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL.


Q19. How will you delete duplicating rows from a base table?

ANS:
delete from table_name where rowid not in (select max(rowid) from table group by duplicate_values_field_name); or delete duplicate_values_field_name dv from table_name ta where rowid <(select min(rowid) from table_name tb where ta.dv=tb.dv);


Q20. What is a view?

ANS:
A view is stored procedure based on one or more tables, its a virtual table.


Q21. How you will avoid duplicating records in a query?

ANS:
By using DISTINCT


Q22. What are cursor attributes?

ANS:
-%ROWCOUNT
-%NOTFOUND
-%FOUND
-%ISOPEN


Q23. What is a transaction?

ANS:
Transaction is logical unit between two commits and commit and rollback.


Q24. What is the Sub query?

ANS:
Sub query is a query whose return values are used in filtering conditions of the main query.


Q25. Can Full Backup be performed when the database is open?

ANS: No.


Q26. Which parameter specified in the DEFAULT STORAGE clause of CREATE TABLESPACE cannot be altered after creating the tablespace?

ANS:
All the default storage parameters defined for the tablespace can be changed using the ALTER TABLESPACE command. When objects are created their INITIAL and MINEXTENS values cannot be changed.


Q27. What is Log Switch?

ANS:
The point at which ORACLE ends writing to one online redo log file and begins writing to another is called a log switch.


Q28. What is Current record attribute property?

ANS:
Specifies the named visual attribute used when an item is part of the current record. Current Record Attribute is frequently used at the block level to display the current row in a multi-record If you define an item-level Current Record Attribute, you can display a pre-determined item in a special color when it is part of the current record, but you cannot dynamically highlight the current item, as the input focus changes.


Q29. What is On-line Redo Log?

ANS:
The On-line Redo Log is a set of row or more on-line redo files that record all committed changes made to the database. Whenever a transaction is committed, the corresponding redo entries temporarily stores in redo log buffers of the SGA are written to an on-line redo log file by the background process LGWR. The on-line redo log files are used in cyclical fashion.


Q30. Can you set default font in forms?

ANS:
Yes. Change windows registry (regedit). Set form 45_font to the desired font.
_break


Q31. Can u port applications across the platforms? How?

ANS:
Yes we can port applications across platforms. Consider the form developed in a windows system. The form would be generated in unix system by using f45gen my_form.fmb scott/tiger.


Q32. Difference between database triggers and form triggers.

ANS:
-Data base trigger(DBT) fires when a DML operation is performed on a data base table. Form trigger(FT) Fires when user presses a key or navigates between fields on the screen
-Can be row level or statement level No distinction between row level and statement level.
-Can manipulate data stored in Oracle tables via SQL Can manipulate data in Oracle tables as well as variables in forms.
-Can be fired from any session executing the triggering DML statements. Can be fired only from the form that define the trigger.
-Can cause other database triggers to fire. Can cause other database triggers to fire, but not other form triggers.


Q33. What is use of a cursor variable? How it is defined?

ANS:
A cursor variable is associated with different statements at run time, which can hold different values at run time. Static cursors can only be associated with one run time query. A cursor variable is reference type (like a pointer in C).
Declaring a cursor variable:
TYPE type_name IS REF CURSOR RETURN return_type type_name is the name of the reference type,return_type is a record type indicating the types of the select list that will eventually be returned by the cursor variable.


Q34. What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?

ANS: 1,000,00


Q35. How do you find the number of rows in a Table?

ANS:
By generating SQL to ANALYZE TABLE table_name COUNT STATISTICS by querying Oracle System Catalogues (e.g. USER_TABLES or ALL_TABLES).
The best answer is to refer to the utility which Oracle released which makes it unnecessary to do ANALYZE TABLE for each Table individually.


Q36. There is a % sign in one field of a column. What will be the query to find it?

ANS:  Should be used before %.


Q37. What is ON DELETE CASCADE?

ANS:
When ON DELETE CASCADE is specified ORACLE maintains referential integrity by automatically removing dependent foreign key values if a referenced primary or unique key value is removed.


Q38. What is the fastest way of accessing a row in a table?

ANS: Using ROWID.CONSTRAINTS


Q39. What is difference between TRUNCATE & DELETE?

ANS:
TRUNCATE commits after deleting entire table i.e., can not be rolled back. Database triggers do not fire on TRUNCATEDELETE allows the filtered deletion. Deleted records can be rolled back or committed. Database triggers fire on DELETE.


Q40. What are the advantages of VIEW?

ANS:
To protect some of the columns of a table from other users. To hide complexity of a query. To hide complexity of calculation.


Q41. How will you activate/deactivate integrity constraints?

ANS:
The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE constraint/DISABLE constraint.


Q42. Where the integrity constraints are stored in Data Dictionary?

ANS:
The integrity constraints are stored in USER_CONSTRAINTS.


Q43. Difference between VAT and Property Class. 

ANS:
Imp Named visual attributes define only font, color, and pattern attributes; property classes can contain these and any other properties.
You can change the appearance of objects at runtime by changing the named visual attribute programmatically; property class assignment cannot be changed programmatically. When an object is inheriting from both a property class and a named visual attribute, the named visual attribute settings take precedence, and any visual attribute properties in the class are ignored.


Q44. What is OLE automation?

ANS:
OLE automation allows an OLE server application to expose a set of commands and functions that can be invoked from an OLE container application. OLE automation provides a way for an OLE container application to use the features of an OLE server application to manipulate an OLE object from the OLE container environment. (FORMS_OLE)


Q45. What is transactional trigger property?

ANS:
Identifies a block as transactional control block. i.e. non - database block that oracle forms should manage as transactional block.(NON-ORACLE datasource) default - FALSE.


Q46. What does invoke built-in do?

ANS:
This procedure invokes a method.
Syntax:
PROCEDURE OLE2.INVOKE
(object obj_type,
method VARCHAR2,
list list_type := 0);
Parameters:
Object is an OLE2 Automation Object.
Method is a method (procedure) of the OLE2 object.
List is the name of an argument list assigned to the OLE2.CREATE_ARGLIST function.


Q47. How to access the current value and next value from a sequence? Is it possible to access the current value in a session before accessing next value?

ANS:
Sequence name CURRVAL, Sequence name NEXTVAL. It is not possible. Only if you access next value in the session, current value can be accessed


Q48. What are the usages of SAVEPOINTS value in a session before accessing next value?

ANS:
SAVE POINTS are used to subdivide a transaction into smaller parts. It enables rolling back part of a transaction. Maximum of five save points are allowed.


Q49. What is ROWID in a session before accessing next value?

ANS:
ROWID is a pseudo column attached to each row of a table. It is 18 character long, blockno, rownumber are the components of ROWID.


Q50. Explain Connect by Prior in a session before accessing next value.

ANS:
Retrieves rows in hierarchical order.e.g. select empno, ename from emp where.


Q51. How many LONG columns are allowed in a table? Is it possible to use LONG columns in WHERE clause or ORDER BY?

ANS:
Only one LONG columns is allowed. It is not possible to use LONG column in WHERE or ORDER BY clause.


Q52. What is Referential Integrity?

ANS:
Maintaining data integrity through a set of rules that restrict the values of one or more columns of the tables based on the values of primary key or unique key of the referenced table.


Q53. What is a join? Explain the different types of joins?

ANS:
Join is a query which retrieves related columns or rows from multiple tables. 
Self Join - Joining the table with itself. 
Equi Join - Joining two tables by equating two common columns. 
Non-Equi Join - Joining two tables by equating two common columns.
Outer Join - Joining two tables in such a way that query can also retrieve rows that do not have corresponding join value in the other table.


Q54. If an unique key constraint on DATE column is created, will it validate the rows that are inserted with SYSDATE?

ANS:
It wont, Because SYSDATE format contains time attached with it.


Q55. How does one stop and start the OMS? 

ANS:
Use the following command sequence to stop and start the OMS (Oracle Management Server):

oemctl start oms
oemctl status oms sysman/oem_temp
oemctl stop oms sysman/oem_temp

Windows NT/2000 users can just stop and start the required services. The default OEM administrator is sysman with a password of oem_temp.
NOTE: Use command oemctrl instead of oemctl for Oracle 8i and below.


Q56. What is an Integrity Constraint?

ANS:
Integrity constraint is a rule that restricts values to a column in a table.


Q57. How does one create a repository? 

ANS:
For OEM v2 and above, start the Oracle Enterprise Manager Configuration Assistant (emca on Unix) to create and configure the management server and repository. Remember to setup a backup for the repository database after creating it.


Q58. If a View on a single base table is manipulated will the changes be reflected on the base table?

ANS:
If changes are made to the tables which are base tables of a view will the changes be reference on the view.


Q59. Create an OEM V1.x repository on Windows NT.

ANS:
. Create a tablespace that would hold the repository data. A size between 200- 250 MB would be ideal. Let us call it Dummy_Space.
. Create an Oracle user who would own this repository. Assign DBA, SNMPAgent, Exp_Full_database, Imp_Full_database roles to this user. Lets call this user Dummy_user. Assign Dummy_Space as the default tablespace.
. Create an operating system user with the same name as the Oracle username. I.e. Dummy_User. Add Log on as a batch job under advanced rights in User manager.
. Fire up Enterprise manager and log in as Dummy_User and enter the password. This would trigger the creation of the repository. From now on, Enterprise manager is ready to accept jobs.


Q60. What is a database link?

ANS:
Database Link is a named path through which a remote database can be accessed.


Q61. How does one list ones databases in the OEM Console?
 
ANS:
Follow these steps to discover databases and other services from the OEM Console:
1. Ensure the GLOBAL_DBNAME parameter is set for all databases in your LISTENER.ORA file (optional). These names will be listed in the OEM Console. Please note that names entered are case sensitive. A portion of a listener.ora file:
(SID_DESC =
(GLOBAL_DBNAME = DB_name_for_OEM)
(SID_NAME = ...
2. Start the Oracle Intelligent Agent on the machine you want to discover. See section How does one start the Oracle Intelligent Agent?
3. Start the OEM Console, navigate to menu Navigator/ Discover Nodes. The OEM Discovery Wizard will guide you through the process of discovering your databases and other services.


Q62. What is CYCLE/NO CYCLE in a Sequence?

ANS:
CYCLE specifies that the sequence continues to generate values after reaching either maximum or minimum value. After pan ascending sequence reaches its maximum value, it generates its minimum value. After a descending sequence reaches its minimum, it generates its maximum. NO CYCLE specifies that the sequence cannot generate more values after reaching its maximum or minimum value.


Q63. What is correlated sub-query?

ANS:
Correlated sub query is a sub query which has reference to the main query.


Q64. What are the data types allowed in a table?

ANS:
CHAR,VARCHAR2,NUMBER,DATE,RAW,LONG and LONG RAW.


Q65. What is difference between CHAR and VARCHAR2? What is the maximum SIZE allowed for each type?

ANS:
CHAR pads blank spaces to the maximum length. VARCHAR2 does not pad blank spaces. For CHAR it is 255 and 2000 for VARCHAR2.


Q66. Can a view be updated/inserted/deleted? If Yes, under what conditions?

ANS:
A View can be updated/deleted/inserted if it has only one base table if the view is based on columns from one or more tables then insert, update and delete is not possible.


Q67. What are the different types of Co ordinations of the Master with the Detail block?

ANS:
POPULATE_GROUP(function)
POPULATE_GROUP_WITH_QUERY(function)
SET_GROUP_CHAR_CELL(procedure)
SET_GROUP_DATE_CELL(procedure)
SET_GROUP_NUMBER_CELL(procedure)


Q68. Use the ADD_GROUP_COLUMN function to add a column to a record group that was created at design time? I) TRUE II)FALSE

ANS: II) FALSE


Q69. Use the ADD_GROUP_ROW procedure to add a row to a static record group? I) TRUE II) FALSE

ANS: I) FALSE


Q70. Using maxvalue.sql, Select the Nth Highest value from a table?

ANS:
select level, max(col_name) from my_table where level = &n connect by prior (col_name) > col_name)
group by level;
Example:
Given a table called emp with the following columns:
-- id number
-- name varchar2(20)
-- sal number
--
-- For the second highest salary:
-- select level, max(sal) from emp
-- where level=2
-- connect by prior sal > sal
-- group by level


Q71. Find out nth highest salary from emp table?

ANS:
SELECT DISTINCT (a.sal) FROM EMP A WHERE &N = (SELECT COUNT (DISTINCT (b.sal)) FROM EMP B WHERE a.sal<=b.sal);
For Eg:-
Enter value for n: 2
SAL
---------
3700


Q72. Suppose a customer table is having different columns like customer no, payments. What will be the query to select top three max payments?

ANS:
SELECT customer_no, payments from customer C1
WHERE 3<=(SELECT COUNT(*) from customer C2
WHERE C1.payment <= C2.payment)


Q73. How you will avoid your query from using indexes?

ANS:

SELECT * FROM emp

Where emp_no+ =12345;
i.e you have to concatenate the column name with space within codes in the where condition.

SELECT /*+ FULL(a) */ ename, emp_no from emp
where emp_no=1234;

i.e using HINTS


Q74. What utility is used to create a physical backup?

ANS:
Either rman or alter tablespace begin backup will do..


Q75. What is a Transaction in Oracle?

ANS:
A transaction is a Logical unit of work that compromises one or more SQL Statements executed by a single User. According to ANSI, a transaction begins with first executable statement and ends when it is explicitly committed or rolled back.


Q76. What are Procedure, functions and Packages?

ANS:
Procedures and functions consist of set of PL/SQL statements that are grouped together as a unit to solve a specific problem or perform set of related tasks.
Procedures do not Return values while Functions return one One Value Packages :: Packages Provide a method of encapsulating and storing related procedures, functions, variables and other Package Contents


Q77. What are Database Triggers and Stored Procedures?

ANS:
Database Triggers :: Database Triggers are Procedures that are automatically executed as a result of insert in, update to, or delete from table.
Database triggers have the values old and new to denote the old value in the table before it is deleted and the new indicated the new value that will be used. DT are useful for implementing complex business rules which cannot be enforced using the integrity rules. We can have the trigger as Before trigger or After Trigger and at Statement or Row level. e.g:: operations insert, update, delete 3 before, after 3*2 A total of 6 combinations
At statement level (once for the trigger) or row level( for every execution ) 6 * 2 A total of 12. Thus a total of 12 combinations are there and the restriction of usage of 12 triggers has been lifted from Oracle 7.3 Onwards.

Stored Procedures :: Stored Procedures are Procedures that are stored in Compiled form in the database. The advantage of using the stored procedures is that many users can use the same procedure in compiled and ready to use format.


Q78. How many Integrity Rules are there and what are they?

ANS:
There are Three Integrity Rules. They are as follows ::
a) Entity Integrity Rule :: The Entity Integrity Rule enforces that the Primary key cannot be Null
b) Foreign Key Integrity Rule :: The FKIR denotes that the relationship between the foreign key and the primary key has to be enforced. When there is data in Child Tables the Master tables cannot be deleted.
c) Business Integrity Rules :: The Third Integrity rule is about the complex business processes which cannot be implemented by the above 2 rules.


Q79. What are the Various Master and Detail Relation ships?

ANS:
The various Master and Detail Relationship are
a) Non Isolated :: The Master cannot be deleted when a child is excisting
b) Isolated :: The Master can be deleted when the child is excisting
c) Cascading :: The child gets deleted when the Master is deleted.


Q80. What are the Various Block Coordination Properties?

ANS:
The various Block Coordination Properties are
a) Immediate Default Setting. The Detail records are shown when the Master Record are shown.
b) Deffered with Auto Query Oracle Forms defer fetching the detail records until the operator navigates to the detail block.
c) Deffered with No Auto Query The operator must navigate to the detail block and explicitly execute a query


Q81. How does one change an Oracle users password?
 
ANS:
Issue the following SQL command:
ALTER USER IDENTIFIED BY ;
From Oracle8 you can just type password from SQL*Plus, or if you need to change another users password, type password user_name. Look at this example:
SQL> password
Changing password for SCOTT
Old password:
New password:
Retype new password:


Q82. How does one create and drop database users?

ANS:
Look at these examples:
CREATE USER scott
IDENTIFIED BY tiger -- Assign password
DEFAULT TABLESACE tools -- Assign space for table and index segments
TEMPORARY TABLESPACE temp; -- Assign sort space
DROP USER scott CASCADE; -- Remove user
After creating a new user, assign the required privileges:
GRANT CONNECT, RESOURCE TO scott;
GRANT DBA TO scott; -- Make user a DB Administrator
Remember to give the user some space quota on its tablespaces:
ALTER USER scott QUOTA UNLIMITED ON tools;


Q83. What are snap shots and views?

ANS:
Snapshots are mirror or replicas of tables. Views are built using the columns from one or more tables. The Single Table View can be updated but the view with multi table cannot be updated


Q84. What are the OOPS concepts in Oracle?

ANS:
Oracle does implement the OOPS concepts. The best example is the Property Classes. We can categorise the properties by setting the visual attributes and then attach the property classes for the objects. OOPS supports the concepts of objects and classes and we can consider the property classes as classes and the items as objects


Q85. What is the difference between candidate key, unique key and primary key?

ANS:
Candidate keys are the columns in the table that could be the primary keys and the primary key is the key that has been selected to identify the rows. Unique key is also useful for identifying the distinct rows in the table.


Q86. What is concurrency?

ANS:
Concurrency is allowing simultaneous access of same data by different users. Locks useful for accessing the database are
a) Exclusive
The exclusive lock is useful for locking the row when an insert, update or delete is being done. This lock should not be applied when we do only select from the row.
b) Share lock
We can do the table as Share_Lock as many share_locks can be put on the same resource.


Q87. What are Previleges and Grants?

ANS:
Previleges are the right to execute a particular type of SQL statements. e.g :: Right to Connect, Right to create, Right to resource.
Grants are given to the objects so that the object might be accessed accordingly. The grant has to be given by the owner of the object.


Q88. What is physical Storage of the Data?

ANS:
The finest level of granularity of the data base are the data blocks.
Data Block :: One Data Block correspond to specific number of physical database space
Extent :: Extent is the number of specific number of contigious data blocks.
Segments :: Set of Extents allocated for Extents. There are three types of Segments
a) Data Segment :: Non Clustered Table has data segment data of every table is stored in cluster data segment
b) Index Segment :: Each Index has index segment that stores data
c) Roll Back Segment :: Temporarily store undo information


Q89. What are the Pct Free and Pct Used?

ANS:
Pct Free is used to denote the percentage of the free space that is to be left when creating a table. Similarly Pct Used is used to denote the percentage of the used space that is to be used when creating a table
eg.:: Pctfree 20, Pctused 40


Q90. What is Row Chaining?

ANS:
The data of a row in a table may not be able to fit the same data block. Data for row is stored in a chain of data blocks .


Q91. What is a 2 Phase Commit?

ANS:
Two Phase commit is used in distributed data base systems. This is useful to maintain the integrity of the database so that all the users see the same values. It contains DML statements or Remote Procedural calls that reference a remote object. There are basically 2 phases in a 2 phase commit.
a) Prepare Phase :: Global coordinator asks participants to prepare
b) Commit Phase :: Commit all participants to coordinator to Prepared, Read only or abort Reply


Q92. What is the difference between deleting and truncating of tables?

ANS:
Deleting a table will not remove the rows from the table but entry is there in the database dictionary and it can be retrieved But truncating a table deletes it completely and it cannot be retrieved.


Q93. What are mutating tables?

ANS:
When a table is in state of transition it is said to be mutating. eg :: If a row has been deleted then the table is said to be mutating and no operations can be done on the table except select.


Q94. What are Codd Rules?

ANS:
Codd Rules describe the ideal nature of a RDBMS. No RDBMS satisfies all the 12 codd rules and Oracle Satisfies 11 of the 12 rules and is the only Rdbms to satisfy the maximum number of rules.


Q95. What is Normalisation?

ANS:
Normalisation is the process of organising the tables to remove the redundancy. There are mainly 5 Normalisation rules.
a) 1 Normal Form :: A table is said to be in 1st Normal Form when the attributes are atomic
b) 2 Normal Form :: A table is said to be in 2nd Normal Form when all the candidate keys are dependant on the primary key
c) 3rd Normal Form :: A table is said to be third Normal form when it is not dependant transitively


Q96. What is the Difference between a post query and a pre query?

ANS:
A post query will fire for every row that is fetched but the pre query will fire only once.


Q97. Explain Deleting the Duplicate rows in the table.

ANS:
We can delete the duplicate rows in the table by using the Rowid


Q98. Can you disable database trigger? How?

ANS:
Yes. With respect to table
ALTER TABLE TABLE
[[ DISABLE all_trigger ]]


Q99. What is pseudo columns? Name them?

ANS:
A pseudocolumn behaves like a table column, but is not actually stored in the table. You can select from pseudocolumns, but you cannot insert, update, or delete their values. This section describes these pseudocolumns:
* CURRVAL
* NEXTVAL
* LEVEL
* ROWID
* ROWNUM


Q100. What is a view?

ANS:
A view is stored procedure based on one or more tables, it is a virtual table.


Q101. What is the difference between UNIQUE and PRIMARY KEY constraints?

ANS:
A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL.


Q102. How many columns can table have?

ANS:
The number of columns in a table can range from 1 to 254.


Q103. Is space acquired in blocks or extents?

ANS: In extents.


Q104. What is clustered index?

ANS:
In an indexed cluster, rows are stored together based on their cluster key values. Can not applied for HASH.


Q105. What are the data types supported by oracle (INTERNAL)?

ANS:
Varchar2, Number,Char , MLSLABEL.


Q106. What are attributes of cursor?

ANS:
%FOUND, %NOTFOUND, %ISOPEN,%ROWCOUNT


Q107. Can you use select in FROM clause of SQL select?

ANS: Yes


Q108. Which trigger are created when master -detail relay?

ANS:
master delete property
* NON-ISOLATED (default)
a) on check delete master
b) on clear details
c) on populate details
* ISOLATED
a) on clear details
b) on populate details
* CASCADE
a) per-delete
b) on clear details
c) on populate details


Q109. What are object group?

ANS:
An object group is a container for a group of objects. You define an object group when you want to package related objects so you can copy or reference them in another module.


Q110. What are referenced objects?

ANS:
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.


Q111. Can you store objects in library?

ANS:
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object.


Q112. Is forms 4.5 object oriented tool? why?

ANS:
yes , partially. 1) PROPERTY CLASS - inheritance property 2) OVERLOADING : procedures and functions.


Q113. Can you issue DDL in forms?

ANS:
yes, but you have to use FORMS_DDL.
Referencing allows you to create objects that inherit their functionality and appearance from other objects. Referencing an object is similar to copying an object, except that the resulting reference object maintains a link to its source object. A reference object automatically inherits any changes that have been made to the source object when you open or regenerate the module that contains the reference object. Any string expression up to 32K:
- a literal
- an expression or a variable representing the text of a block of dynamically created PL/SQL code
- a DML statement or
- a DDL statement
Restrictions:
The statement you pass to FORMS_DDL may not contain bind variable references in the string, but the values of bind variables can be concatenated into the string before passing the result to FORMS_DDL


Q114. What is SECURE property?

ANS:
- Hides characters that the operator types into the text item. This setting is typically used for password protection.


Q115. Can you store pictures in database? How?

ANS: Yes, in long Raw data type.


Q116. What are property classes? Can property classes have trigger?

ANS:
Property class inheritance is a powerful feature that allows you to quickly define objects that conform to your own interface and functionality standards. Property classes also allow you to make global changes to applications quickly. By simply changing the definition of a property class, you can change the definition of all objects that inherit properties from that class.
Yes. All type of triggers.


Q117. If you have property class attached to an item and you have same trigger written for the item. Which will fire first?

ANS:
Item level trigger fires, If item level trigger fires, property level trigger wont fire. Triggers at the lowest level are always given the first preference. The item level trigger fires first and then the block and then the Form level trigger.


Q118. Can a button have icon and label at the same time?

ANS: NO


Q119. What is mouse navigate property of button?

ANS:
When Mouse Navigate is True (the default), Oracle Forms performs standard navigation to move the focus to the item when the operator activates the item with the mouse.
When Mouse Navigate is set to False, Oracle Forms does not perform navigation (and the resulting validation) to move to the item when an operator activates the item with the mouse.


Q120. What is FORMS_MDI_WINDOW?

ANS:
forms run inside the MDI application window. This property is useful for calling a form from another one.


Q121. What are timers? When when-timer-expired does not fire?

ANS:
The When-Timer-Expired trigger can not fire during trigger, navigation, or transaction processing.


Q122. Can object group have a block?

ANS:
Yes, object group can have block as well as program units.


Q123. How many types of canvases are there?

ANS:
There are 2 types of canvases called as Content and Stack Canvas. Content canvas is the default and the one that is used mostly for giving the base effect. It is like a plate on which we add items and stacked canvas is used for giving 3 dimensional effect.


Q124. What are user-exits?

ANS:
It invokes 3GL programs.


Q125. Can you pass values to-and-fro from foreign function? How?

ANS:
Yes . You obtain a return value from a foreign function by assigning the return value to an Oracle Forms variable or item. Make sure that the Oracle Forms variable or item is the same data type as the return value from the foreign function.

After assigning an Oracle Forms variable or item value to a PL/SQL variable, pass the PL/SQL variable as a parameter value in the PL/SQL interface of the foreign function. The PL/SQL variable that is passed as a parameter must be a valid PL/SQL data type; it must also be the appropriate parameter type as defined in the PL/SQL interface.


Q126. What is IAPXTB structure?

ANS:
The entries of Pro * C and user exits and the form which simulate the proc or user_exit are stored in IAPXTB table in d/b.


Q127. Can you call WIN-SDK through user exits?

ANS: YES.


Q128. Does user exits supports DLL on MSWINDOWS?

ANS: YES.


Q129. What is path setting for DLL?

ANS:
Make sure you include the name of the DLL in the FORMS45_USEREXIT variable of the ORACLE.INI file, or rename the DLL to F45XTB.DLL. If you rename the DLL to F45XTB.DLL, replace the existing F45XTB.DLL in the ORAWINBIN directory with the new F45XTB.DLL.


Q130. How is mapping of name of DLL and function done?

ANS:
The dll can be created using the Visual C++ / Visual Basic Tools and then the dll is put in the path that is defined the registery.


Q131. What is precompiler?

ANS:
It is similar to C precompiler directives.


Q132. Can you connect to non - oracle data source?
 
ANS: Yes.


Q133. What are key-mode and locking mode properties? 

ANS:
Key Mode: Specifies how oracle forms uniquely identifies rows in the database. This is property includes for application that will run against NON-ORACLE datasources .
Key setting unique (default.)
dateable
n-updateable.

Locking mode: Specifies when Oracle Forms should attempt to obtain database locks on rows that correspond to queried records in the form. a) immediate b) delayed


Q134. What are save point mode and cursor mode properties? 

ANS:
Specifies whether Oracle Forms should issue savepoints during a session. This property is included primarily for applications that will run against non-ORACLE data sources. For applications that will run against ORACLE, use the default setting.
Cursor mode - define cursor state across transaction Open/close.


Q135. What are the Back ground processes in Oracle and what are they?

ANS:
There are basically 9 Processes but in a general system we need to mention the first five background processes. They do the house keeping activities for the Oracle and are common in any system.
The various background processes in oracle are
a) Data Base Writer(DBWR) :: Data Base Writer Writes Modified blocks from Database buffer cache to Data Files.This is required since the data is not written whenever a transaction is commited.
b)LogWriter(LGWR) :: LogWriter writes the redo log entries to disk. Redo Log data is generated in redo log buffer of SGA. As transaction commits and log buffer fills, LGWR writes log entries into a online redo log file.
c) System Monitor(SMON) :: The System Monitor performs instance recovery at instance startup.This is useful for recovery from system failure
d)Process Monitor(PMON) :: The Process Monitor peforms process recovery when user Process fails. Pmon Clears and Frees resources that process was using.
e) CheckPoint(CKPT) :: At Specified times, all modified database buffers in SGA are written to data files by DBWR at Checkpoints and Updating all data files and control files of database to indicate the most recent checkpoint
f) Archieves(ARCH) :: The Archiver copies online redo log files to archival storal when they are busy.
g) Recoveror(RECO) :: The Recoveror is used to resolve the distributed transaction in network
h) Dispatcher (Dnnn) :: The Dispatcher is useful in Multi Threaded Architecture
i) Lckn :: We can have upto 10 lock processes for inter instance locking in parallel sql.


Q136. What are the key words Used in Oracle.

ANS:
The Key words that are used in Oracle are ::
a) Committing :: A transaction is said to be committed when the transaction makes permanent changes resulting from the SQL statements.
b) Rollback :: A transaction that retracts any of the changes resulting from SQL statements in Transaction.
c) SavePoint :: For long transactions that contain many SQL statements, intermediate markers or savepoints are declared. Savepoints can be used to divide a transactino into smaller points.
d) Rolling Forward :: Process of applying redo log during recovery is called rolling forward.
e) Cursor :: A cursor is a handle ( name or a pointer) for the memory associated with a specific stament. A cursor is basically an area allocated by Oracle for executing the Sql Statement. Oracle uses an implicit cursor statement for Single row query and Uses Explcit cursor for a multi row query.
f) System Global Area(SGA) :: The SGA is a shared memory region allocated by the Oracle that contains Data and control information for one Oracle Instance.It consists of Database Buffer Cache and Redo log Buffer.
g) Program Global Area (PGA) :: The PGA is a memory buffer that contains data and control information for server process.
g) Database Buffer Cache :: Databese Buffer of SGA stores the most recently used blocks of datatbase data.The set of database buffers in an instance is called Database Buffer Cache.
h) Redo log Buffer :: Redo log Buffer of SGA stores all the redo log entries.
i) Redo Log Files :: Redo log files are set of files that protect altered database data in memory that has not been written to Data Files. They are basically used for backup when a database crashes.
j) Process :: A Process is a thread of control or mechanism in Operating System that executes series of steps.


Q137. What are the Different Optimisation Techniques?

ANS:
The Various Optimisation techniques are
a) Execute Plan :: we can see the plan of the query and change it accordingly based on the indexes
b) Optimizer_hint ::
set_item_property(DeptBlock,OPTIMIZER_HINT,FIRST_ROWS);
Select /*+ First_Rows */ Deptno,Dname,Loc,Rowid from dept
where (Deptno > 25)
c) Optimize_Sql ::
By setting the Optimize_Sql = No, Oracle Forms assigns a single cursor for all SQL statements. This slow down the processing because for evertime the SQL must be parsed whenever they are executed.
f45run module = my_firstform userid = scott/tiger optimize_sql = No
d) Optimize_Tp ::
By setting the Optimize_Tp= No, Oracle Forms assigns seperate cursor only for each query SELECT statement. All other SQL statements reuse the cursor.
f45run module = my_firstform userid = scott/tiger optimize_Tp = No


Q138. Who created all these users in my database? Can I drop this user?
 
ANS:
Oracle creates a number of default database users or schemas when a new database is created. Below are a few of them:

SYS/CHANGE_ON_INSTALL or INTERNAL
Oracle Data Dictionary/ Catalog
Created by:?/rdbms/admin/sql.bsq and various cat*.sql scripts
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
SYSTEM/MANAGER
The default DBA user name (please do not use SYS)
Created by:?/rdbms/admin/sql.bsq
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
OUTLN/OUTLN
Stored outlines for optimizer plan stability
Created by:?/rdbms/admin/sql.bsq
Can password be changed: Yes (Do so right after the database was created)
Can user be dropped: NO
SCOTT/TIGER, ADAMS/WOOD, JONES/STEEL, CLARK/CLOTH and BLAKE/PAPER.
Training/ demonstration users containing the popular EMP and DEPT tables
Created by:?/rdbms/admin/utlsampl.sql
Can password be changed: Yes
Can user be dropped: YES - Drop users cascade from all production environments
HR/HR (Human Resources), OE/OE (Order Entry), SH/SH (Sales History).
Training/ demonstration users containing the popular EMPLOYEES and DEPARTMENTS tables
Created by:?/demo/schema/mksample.sql
Can password be changed: Yes
Can user be dropped: YES - Drop users cascade from all production environments
CTXSYS/CTXSYS
Oracle interMedia (ConText Cartridge) administrator user
Created by:?/ctx/admin/dr0csys.sql
TRACESVR/TRACE
Oracle Trace server
Created by:?/rdbms/admin/otrcsvr.sql
DBSNMP/DBSNMP
Oracle Intelligent agent
Created by:?/rdbms/admin/catsnmp.sql, called from catalog.sql
Can password be changed: Yes - put the new password in snmp_rw.ora file
Can user be dropped: YES - Only if you do not use the Intelligent Agents
ORDPLUGINS/ORDPLUGINS
Object Relational Data (ORD) User used by Time Series, etc.
Created by:?/ord/admin/ordinst.sql
ORDSYS/ORDSYS
Object Relational Data (ORD) User used by Time Series, etc
Created by:?/ord/admin/ordinst.sql
DSSYS/DSSYS
Oracle Dynamic Services and Syndication Server
Created by:?/ds/sql/dssys_init.sql
MDSYS/MDSYS
Oracle Spatial administrator user
Created by:?/ord/admin/ordinst.sql
AURORA$ORB$UNAUTHENTICATED/INVALID

Used for users who do not authenticate in Aurora/ORB
Created by:?/javavm/install/init_orb.sql called from?/javavm/install/initjvm.sql
PERFSTAT/PERFSTAT 
Oracle Statistics Package (STATSPACK) that supersedes UTLBSTAT/UTLESTAT
Created by:?/rdbms/admin/statscre.sql
Remember to change the passwords for the SYS and SYSTEM users immediately after installation!
Except for the user SYS, there should be no problem altering these users to use a different default and temporary tablespace.


Q139. How does one switch to another user in Oracle? 

ANS:
Users normally use the connect statement to connect from one database user to another. However, DBAs can switch from one user to another without a password. Of course it is not advisable to bridge Oracles security, but look at this example: SQL> select password from dba_users where username=SCOTT;

PASSWORD
F894844C34402B67
SQL> alter user scott identified by lion;
User altered.
SQL> connect scott/lion
Connected.
REM Do whatever you like...
SQL> connect system/manager
Connected.
SQL> alter user scott identified by values F894844C34402B67;
User altered.
SQL> connect scott/tiger
Connected.

Note: Also see the su.sql script in the Useful Scripts and Sample Programs Page.


Q140. What are the types of triggers and how the sequence of firing in text item?

ANS:
Triggers can be classified as Key Triggers, Mouse Triggers, Navigational Triggers.
Key Triggers :: Key Triggers are fired as a result of Key action.e.g :: Key-next-field, Key-up,Key-Down
Mouse Triggers :: Mouse Triggers are fired as a result of the mouse navigation.e.g. When-mouse-button-presed,when-mouse-doubleclicked,etc
Navigational Triggers :: These Triggers are fired as a result of Navigation. E.g : Post-Text-item,Pre-text-item.
We also have event triggers like when?new-form-instance and when-new-block-instance.
We cannot call restricted procedures like go_to(?my_block.first_item?) in the Navigational triggers
But can use them in the Key-next-item.
The Difference between Key-next and Post-Text is an very important question. The key-next is fired as a result of the key action while the post text is fired as a result of the mouse movement. Key next will not fire unless there is a key event. The sequence of firing in a text item are as follows ::
a) pre - text
b) when new item
c) key-next
d) when validate
e) post text


Q141. What are record groups? Can record groups created at run-time?

ANS:
A record group is an internal Oracle Forms data structure that has a column/row framework similar to a database table. However, unlike database tables, record groups are separate objects that belong to the form module in which they are defined. A record group can have an unlimited number of columns of type CHAR, LONG, NUMBER, or DATE provided that the total number of columns does not exceed 64K. Record group column names cannot exceed 30 characters.

Programmatically, record groups can be used whenever the functionality offered by a two-dimensional array of multiple data types is desirable.

TYPES OF RECORD GROUP:

Query Record Group A query record group is a record group that has an associated SELECT statement. The columns in a query record group derive their default names, data types, and lengths from the database columns referenced in the SELECT statement. The records in a query record group are the rows retrieved by the query associated with that record group.
Non-query Record Group A non-query record group is a group that does not have an associated query, but whose structure and values can be modified programmatically at runtime.

Static Record Group A static record group is not associated with a query; rather, you define its structure and row values at design time, and they remain fixed at runtime.


Q142. What are OPEN_FORM, CALL_FORM, NEW_FORM? Difference between them.

ANS:
CALL_FORM : It calls the other form. But parent remains active, when called form completes the operation, it releases lock and control goes back to the calling form.
When you call a form, Oracle Forms issues a savepoint for the called form. If the CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms rolls back uncommitted changes to this savepoint.

OPEN_FORM : When you call a form, Oracle Forms issues a savepoint for the called form. If the CLEAR_FORM function causes a rollback when the called form is current, Oracle Forms rolls back uncommitted changes to this savepoint.

NEW_FORM : Exits the current form and enters the indicated form. The calling form is terminated as the parent form. If the calling form had been called by a higher form, Oracle Forms keeps the higher call active and treats it as a call to the new form. Oracle Forms releases memory (such as database cursors) that the terminated form was using.
Oracle Forms runs the new form with the same Runform options as the parent form. If the parent form was a called form, Oracle Forms runs the new form with the same options as the parent form.


Q143. How many types of Sql Statements are there in Oracle?

ANS:
There are basically 6 types of sql statements. They are
a) Data Definition Language (DDL) :: The DDL statements define and maintain objects and drop objects.
b) Data Manipulation Language (DML) :: The DML statements manipulate database data.
c) Transaction Control Statements :: Manage change by DML
d) Session Control :: Used to control the properties of current session enabling and disabling roles and changing .e.g :: Alter Statements,Set Role
e) System Control Statements :: Change Properties of Oracle Instance .e.g:: Alter System
f) Embedded Sql :: Incorporate DDL,DML and T.C.S in Programming Language.e.g:: Using the Sql Statements in languages such as C, Open, Fetch, execute and close


Q144. What is in all those X$ tables? 

ANS:
The following list attempts to describe some x$ tables. The list may not be complete or accurate, but represents an attempt to figure out what information they contain. One should generally not write queries against these tables as they are internal to Oracle, and Oracle may change them without any prior notification.

X$K2GTE2     Kernel 2 Phase Commit Global Transaction Entry Fixed Table
X$K2GTE     Kernel 2 Phase Commit Global Transaction Entry Fixed Table
X$BH     Buffer headers contain information describing the current contents of a piece of the buffer cache
X$KCBCBH     Cache Buffer Current Buffer Header Fixed Table. It can predict the potential loss of decreasing the number of database buffers. The db_block_lru_statistics parameter has to be set to true to gather information in this table.
X$KCVFH     File Header Fixed Table
X$KDNCE     SGA Cache Entry Fixed Table
X$KDNST     Sequence Cache Statistics Fixed Table
X$KDXHS     Histogram structure Fixed Table
X$KDXST     Statistics collection Fixed Table
X$KGHLU     One-row summary of LRU statistics for the shared pool
X$KGLBODY     Derived from X$KGLOB (col kglhdnsp = 2)
X$KGLCLUSTER     Derived from X$KGLOB (col kglhdnsp = 5)
X$KGLINDEX     Derived from X$KGLOB (col kglhdnsp = 4)
X$KGLLC     Latch Clean-up state for library cache objects Fixed Table
X$KGLPN     Library cache pin Fixed Table
X$KGLTABLE     Derived from X$KGLOB (col kglhdnsp = 1)
X$KGLTR     Library Cache Translation Table entry Fixed Table
X$KGLTRIGGER     Derived from X$KGLOB (col kglhdnsp = 3)
X$KGLXS     Library Cache Access Table
X$KKMMD     Fixed table to look at what databases are mounted and their status
X$KKSBV     Cursor Cache Bind Variables
X$KSMSP     Each row represents a piece of memory in the shared pool
X$KSQDN     Global database name
X$KSQST     Enqueue statistics by type
X$KSUCF     Cost function for each Kernel Profile (join to X$KSUPL)
X$KSUPL     Resource Limit for each Kernel Profile
X$KSURU     Resource Usage for each Kernel Profile (join with X$KSUPL)
X$KSQST     Gets and waits for different types of enqueues
X$KTTVS     Indicate tablespace that has valid save undo segments
X$KVII     Internal instance parameters set at instance initialization
X$KVIS     Oracle Data Block (size_t type) variables
X$KVIT     Instance internal flags, variables and parameters that can change during the life of an instance
X$KXFPCDS     Client Dequeue Statistics
X$KXFPCMS     Client Messages Statistics
X$KZDOS     Represent an os role as defined by the operating system
X$KZSRO     Security state Role: List of enabled roles
X$LE     Lock Element: each PCM lock that is used by the buffer cache (gc_db_locks)
X$MESSAGES     Displays all the different messages that can be sent to the Background processes
X$NLS_PARAMETERS     NLS database parameters

Handy X$table queries
Some handy queries based on the X$ memory tables:
. Largest # blocks you can write at any given time:
select kviival write_batch_size
from x$kvii where kviitag = kcbswc;
. See the gets and waits for different types of enqueues:
select * from x$ksqst
where ksqstget > 0;
Oracle Kernel Subsystems
Listed below are some of the important subsystems in the Oracle kernel. This table might help you to read those dreaded trace files and internal messages. For example, if you see messages like this, you will at least know where they come from: OPIRIP: Uncaught error 447. Error stack:
KCF: write/open error block=0x3e800 online=1
OPI     Oracle Program Interface
KK     Compilation Layer - Parse SQL, compile PL/SQL
KX     Execution Layer - Bind and execute SQL and PL/SQL
K2     Distributed Execution Layer - 2PC handling
NPI     Network Program Interface
KZ     Security Layer - Validate privs
KQ     Query Layer
RPI     Recursive Program Interface
KA     Access Layer
KD     Data Layer
KT     Transaction Layer
KC     Cache Layer
KS     Services Layer
KJ     Lock Manager Layer
KG     Generic Layer
KV     Kernel Variables (eg. x$KVIS and X$KVII)
S or ODS     Operating System Dependencies


Q145. How does one enforce strict password control? 

ANS:
By default Oracles security is not extremely good. For example, Oracle will allow users to choose single character passwords and passwords that match their names and user ids. Also, passwords do not ever expire. This means that one can hack an account for years without ever locking the user.
From Oracle8 one can manage passwords through profiles. Some of the things that one can restrict:
. FAILED_LOGIN_ATTEMPTS - failed login attempts before the account is locked
. PASSWORD_LIFE_TIME - limits the number of days the same password can be used for authentication
. PASSWORD_REUSE_TIME - number of days before a password can be reused
. PASSWORD_REUSE_MAX - number of password changes required before the current password can be reused
. PASSWORD_LOCK_TIME - number of days an account will be locked after maximum failed login attempts
. PASSWORD_GRACE_TIME - number of days after the grace period begins during which a warning is issued and login is allowed
. PASSWORD_VERIFY_FUNCTION - password complexity verification script
Look at this simple example:
CREATE PROFILE my_profile LIMIT
PASSWORD_LIFE_TIME 30;
ALTER USER scott PROFILE my_profile


Q146. Define Table Space, Data Files, Parameter File.

ANS:
Table Space :: The table space is useful for storing the data in the database. When a database is created two table spaces are created.
a) System Table space :: This data file stores all the tables related to the system and DBA tables
b) User Table space :: This data file stores all the user related tables
We should have separate table spaces for storing the tables and indexes so that the access is fast.

Data Files:: Every Oracle Data Base has one or more physical data files. They store the data for the database. Every data file is associated with only one database. Once the Data file is created the size cannot change. To increase the size of the database to store more data we have to add data file.

Parameter Files :: Parameter file is needed to start an instance.A parameter file contains the list of instance configuration parameters e.g.::
db_block_buffers = 500
db_name = ORA7
db_domain = u.s.acme lang


Q147. Define Control Files.

ANS:
Control Files :: Control files record the physical structure of the data files and redo log files

They contain the Db name, name and location of dbs, data files, redo log files and time stamp.


  
   






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