Tuesday, November 23, 2010


Oracle  Concepts and Architecture Database Structures.

1.What are the components of Physical database structure of Oracle Database?.
ORACLE database is comprised of three types of files. One or more Data files, two are more Redo Log files, and one or more Control files.
2. What are the components of Logical database structure of ORACLE database?
Tablespaces and the Database's Schema Objects.
3. What is a Tablespace?
A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to group related logical structures together.
4. What is SYSTEM tablespace and When is it Created?
Every ORACLE database contains a tablespace named SYSTEM, which is automatically  created when the database is created. The SYSTEM tablespace always contains the data dictionary tables for the entire database.
5. Explain the relationship among Database, Tablespace and Data file.
Each databases logically divided into one or more tablespaces One or more data files are explicitly created for each tablespace.
6. What is schema?
A schema is collection of database objects of a User.
7. What are Schema Objects ?
Schema  objects  are  the  logical  structures  that  directly refer to the database's  data.  Schema  objects include tables, views, sequences, synonyms, indexes,  clusters,  database  triggers, procedures, functions packages anddatabase links.
8. Can objects of the same Schema reside in different tablespaces.?
9. Can a Tablespace hold objects from different Schemes ?
10. what is Table ?
A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.
11. What is a View ?
A  view  is  a  virtual  table. Every view has a Query attached to it. (The Query  is  a  SELECT  statement that identifies the columns and rows of the table(s) the view uses.)
12. Do  View contain Data ?
Views do not contain or store data.
13. Can a  View based on another View ?
14. What are the advantages of Views ?
Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table. Hide data complexity. Simplify commands for the user. Present the data in a different perceptive from that of the base table. Store complex queries.
15. What is a Sequence ?
A  sequence generates a serial list of unique numbers for numerical columns of a database's tables.
16.  What is a Synonym ?
A synonym is an alias for a table, view, sequence or program unit.
17. What are the type of Synonyms?
There are two types of Synonyms Private and Public.
18. What is a Private Synonyms ?
A Private Synonyms can be accessed only by the owner.
19. What is a Public Synonyms ?
A Public synonyms can be accessed by any user on the database.
20. What are synonyms used for ?
Synonyms are used to : Mask the real name and owner of an object.
Provide public access to an object
Provide location transparency for tables, views or program units of a remote database.
Simplify the SQL statements for database users.
21. What is an Index ?
An Index is  an optional structure associated with a table to have direct access  to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.
22.  How are Indexes Update ?
Indexes  are  automatically maintained and used by ORACLE. Changes to table data are automatically incorporated into all relevant indexes.
23. What are Clusters ?
Clusters  are  groups  of  one or more tables physically stores together to share common columns and are often used together.
24. What is cluster Key ?
The related columns of the tables in a cluster is called the Cluster Key.
25. What is Index Cluster ?
A Cluster with an index on the Cluster Key.
26. What is Hash Cluster ?
A  row  is  stored in a hash cluster based on the result of applying a hash function  to  the  row's cluster key value. All rows with the same hash key value are stores together on disk.
27. When can Hash Cluster used ?
Hash clusters are better choice when a table is often queried with equality queries.  For  such  queries the specified cluster key value is hashed. The resulting  hash  key  value points directly to the area on disk that stores the specified rows.
28. What is  Database Link ?
A database link is a named object that describes a "path" from one database to another.
29. What are the types of Database Links ?
Private Database Link, Public Database Link & Network Database Link.
30. What is Private Database Link ?
Private  database  link  is created on behalf of a specific user. A private database  link  can  be  used  only  when the owner of the link specifies a global  object  name in a SQL statement or in the definition of the owner's views or procedures.
31. What is Public Database Link ?
Public database link is created for the special user group PUBLIC. A public database  link  can  be  used  when  any  user  in  the associated database specifies a global object name in a SQL  statement or object definition.
32.  What is Network Database link ?
Network database link is created and managed by a network domain service. A network  database  link  can  be  used when any user of any database in the network  specifies  a  global  object  name  in  a  SQL statement or object definition.
33. What is Data Block ?
ORACLE database's data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk.
34. How to define Data Block size ?
A data block size is specified for each ORACLE database when the database is  created. A database users and allocated free database space in ORACLE data blocks.  Block size is specified in INIT.ORA file and cann't be changed latter.
35. What is Row Chaining ?
In  Circumstances,  all of the data for a row in a table may not be able to fit  in  the  same  data  block. When this occurs , the data for the row is stored in a chain of data block (one or more) reserved for that segment.
36. What is an Extent ?
An   Extent  is  a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information.
37.  What is a Segment ?
A segment is a set of extents allocated for a certain logical structure.
38. What are the different type of Segments ?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.
39. What is a Data Segment ?
Each  Non-clustered  table  has  a data segment. All of the table's data is stored in the extents of its data segment. Each cluster has a data segment. The  data  of  every  table  in the cluster is stored in the cluster's data segment.
40. What is an Index Segment ?
Each Index has an Index segment that stores all of its data.
41. What is  Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily store "undo" information.
42. What are the uses of Rollback Segment ?
Rollback Segments are used : To  generate  read-consistent database information during database recovery to rollback uncommitted transactions for users.
43. What is a Temporary Segment ?
Temporary segments are created by ORACLE when a SQL statement needs a temporary  work  area  to  complete  execution. When the statement finishes execution, the  temporary  segment  extents are released to the system for future use.
44. What is a Data File ?
Every  ORACLE  database  has  one or more physical data files. A database's data  files  contain  all  the  database data. The data of logical database structures  such  as  tables  and  indexes is physically stored in the data files allocated for a database.
45. What are the Characteristics of Data Files ?
A  data  file  can be associated with only one database. Once created a data file can't change size.
One  or  more  data  files form a logical unit of database storage called a tablespace.
46. What is a Redo Log ?
The  set  of  Redo  Log  files  for a database is collectively known as the database's redo log.
47. What is the function of Redo Log ?
The Primary function of the redo log is to record all changes made to data.
48. What is the use of Redo Log Information ?
The Information in a redo log file is used only to recover the database from a system or media failure prevents database data from being written to a database's data files.
49. What does a Control file Contain ?
A Control file records the physical structure of the database. It contains the following information.
Database Name
Names and locations of a database's files and redo log files.
Time stamp of database creation.
50. What is the use of Control File ?
When an instance of an ORACLE database is started, its control file is used to  identify  the  database  and  redo  log  files  that must be opened for database operation to proceed. It is also used in database recovery.
51. What is a Data Dictionary ?
The data dictionary of an ORACLE database is a set of tables and views that are used as a read-only reference about the database. It stores information about both the logical and physical structure of the database, the valid users of an ORACLE database, integrity constraints defined for tables in the database and space allocated for a schema object and how much of it is being used.
52. What is an Integrity Constrains ?
An integrity constraint is a declarative way to define a business rule for a column of a table.
53.  Can an Integrity Constraint be enforced on a table if some existing table data does not satisfy the constraint ?
54.  Describe the different type of Integrity Constraints supported by ORACLE ?
NOT NULL Constraint    - Disallows NULLs in a table's column.
UNIQUE Constraint      - Disallows duplicate values in a column or set of columns.
PRIMARY KEY Constraint - Disallows duplicate values and NULLs in a column or set of columns.
FOREIGN KEY Constrain - Require each value in a column or set of columns match a value in a related table's UNIQUE or PRIMARY KEY.
CHECK Constraint      - Disallows values that do not satisfy the logical expression of the constraint.
55. What is difference between UNIQUE constraint and PRIMARY KEY constraint ?
A  column  defined  as UNIQUE can contain NULLs while a column defined as PRIMARY KEY can't contain Nulls.
56. Describe Referential Integrity ?
A rule defined on a column (or set of columns) in one table that allows the insert  or  update  of  a  row  only  if the value for the column or set of columns  (the  dependent  value)  matches  a value in a column of a related table   (the  referenced  value).  It  also  specifies  the  type  of  data manipulation  allowed  on referenced data and the action to be performed on dependent data as a result of any action on referenced data.
57.  What  are  the  Referential actions supported by FOREIGN KEY integrity constraint ?
UPDATE  and  DELETE  Restrict - A referential integrity rule that disallows the update or deletion of referenced data.
DELETE  Cascade - When a referenced row is deleted all associated dependent rows are deleted.
58. What is self-referential integrity constraint ?
If  a  foreign  key  reference  a  parent  key  of the same table is called self-referential integrity constraint.
59. What are the Limitations of a CHECK Constraint ?
The  condition  must  be a Boolean expression evaluated using the values in the row being inserted or updated and can't contain subqueries, sequence, the SYSDATE,UID,USER  or  USERENV  SQL functions, or the pseudo columns LEVEL or ROWNUM.
60.  What is the maximum number of CHECK constraints that can be defined on a column ?
No Limit.
61. What constitute an ORACLE Instance ?
SGA  and  ORACLE  background  processes constitute an ORACLE instance. (or) Combination of memory structure and background process.

Basic Questions and Answers
1. What do you mean by PC?
Personal computer
2. A machine that uses binary logic to process information is ............
3. Computer we use for personal use is called
4. On railway station computers are used for
5. With computer we can
Write letters, Make drawings, Play games
6. Engineers take the help of computers to
design maps of buildings
7. Devices that allow you to put information into the computer
8. The case of outer shell of the CPU is the
9. Rohit has a personal computer. He has added a new hardware to it. It can be ......
10. The part of computer that we can see or touch is
11. The information you save into the computer is called..................
12. ........... is needed as input by a computer to work.
13. A keyboard is ................ device.
14. Which is the standard input device 
15. An input device that has keys for letters, numbers, and symbols is ..................
16. Without this, we cannot interact with a computer. What is this ?
Input device
17. Which of the following item is NOT an input device?
A. Keyboard B. Mouse
C. Printer D. Joy stick
Ans: Printer (C)
18. A piece of hardware that looks like a TV
19. A hand-held input device that moves the arrow pointer on the screen and lets you select items by clicking on it.
20. Input device used to select or highlight is
21. Computer screen can be named as
Monitor and VDU (Visual Display Unit)
22. The computer monitor is which type of device?
23. Which is the TV-like part of the computer?
24. An output device that produces a hard copy of the information on your screen is ..................
25. An output device that displays text and graphics generated by a computer is ........
Slide show
26. It displays the data and the instructions when they are typed on the keyboard. It is
27. VDU is
28. Which one of the following devices is needed to hear multimedia software ?
29. Which among the following is not an output device?
A. Printer B. Speakers
C. Keyboard D. Monitor
Ans: Keyboard (C)
30. Output from a printer is
31. Which one of the following is called the ‘brain’ of the computer?
32. The main chip in a computer that processes digital information and can do millions of calculations per second is 
33. CPU means
Central Processing Unit
34. It controls all parts of computers, namely monitor, keyboard and mouse. It is
35. Which of the following is a component of CPU ?
36. Information can be stored on all of the following except –
A. A diskette
B. The keyboard
D. The hard drive
Ans: Key Board (B)
37. Find the odd one out.
A. Central processing unit
B. Arithmetical and logical unit
C. Control unit
D. Memory unit
Ans: Central Processing Unit
38. Processing speed of computer is dependent on
39. The part of CPU which is capable of performing addition, subtraction,
multiplication, division as well as comparison is
40. A computer’s temporary memory is
42. This is a permanent storage device.
Hard disk
43. A place in the computer system where data and programs are temporarily stored
44. The primary device that a computer uses to store information is ..............
Hard drive
45. The smallest item of useful information a computer can handle
46. Eight bits of data is equal to one
48. A plastic coated disk that stores digital data on the surface and is read by
scanning the surface with a laser beam is called .....................
49. The primary device that a computer uses to store programs and files. Generally “C:” drive on PC
Hard drive
50. It puts information into the computer. (Examples: keyboard, mouse, scanner,
digital camera, microphone.)
Input device
51. Information can be stored on all of the following except ................
A. A diskette B. The hard drive
C. The keyboard D. A CD-ROM
Ans: Keyboard
52. Jyoti has a newly formatted floppy disk that holds 1.44 MB. Which file will NOT fit on this disk ?
A. Amphibians 1.00 MB
B. Reptiles 1.80 MB
C. Fish 1.30 MB
D. Birds 1.10 MB
Ans: B
53. 1024 bytes equals
1 Kilo byte (KB)
54. 8 bits equal
1 byte
55. 1 KB is equal to ..............
1024 bytes
56. A device that reads the information contained on a disk and transfers it to the
computer’s memory.
Disk drive
57. The information is stored in it as long as computer is on. The moment the computer is switched off the date, instructions, and information are lost. It is
58. A small device that is used to control pointer on the screen is called
59. Dinesh has no printer to print his report. He wants to take it to Vipul’s computer
because he has a printer. He should save his report on a ....
Pen drive, CD, Floppy
60. The device is used to listen music and sound through computer. Identify it
61. In a sky fight video game, for moving a plane, which device is more easy to use ?
62. CD-ROM stands for ................
CD-read only memory
63. Identify the device which is used to play games in computers
64. Which one of the following device is used to scan pictures in the computer?
65. The device that keeps a computer running for several minutes after a power failure is known as ...........
66. UPS is the short name for .............
Uninterrupted Power Supply
67. A peripheral input device that uses light sensing equipment to read paper images
and translates the images into digital information is called .................
68. An external device that plugs into a computer, such as a printer, modem,
scanner, digital camera or speaker.
69. It takes pictures without film and stores snapshots as digital files in its memory.
The picture files are transferred to a computer through a cable or disk.
Digital camera
70. Scanner is a machine that
Reproduces images onto a computer 16. Which one of the following devices could be used to place a photograph into a document? Scanner
71. A printer is needed to .................
Create hard copies of documents
72. Joystick is
Input Device
73. You have a great picture of yours when you were 2 yrs old., that you want to send
to your friend. The way to put the picture into the computer is .............. .
By scanning it
74. Trisha needs to put pictures of the asketball team to place in tomorrow’s
school newspaper. The fastest way to d this would be to use a ––
75. Maya’s teacher bought come new software, which is shown here. Where in
the computer will she put this in order to run the new
76. Pallavi has colour pictures in her document, and a black and white printer.
What will happen to the pictures when she prints the document on her printer?
They will print as if they were black and white
77. Data can be fed into a CD using
Compact disk

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