INTERVIEW 2

 21. What are the type of Synonyms? - There are two types of Synonyms Private and Public

22. What is a Redo Log? - The set of Redo Log files YSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.

23. What is an Index Segment? - Each Index has an Index segment that stores all of its data.

24. 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

25. What are the different type of Segments? - Data Segment, Index Segment, Rollback Segment and Temporary Segment.

26. What are Clusters? - Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

27. What is an Integrity Constrains? - An integrity constraint is a declarative way to define a business rule for a column of a table.

28. 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.

29. What is an Extent? - An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.

30. 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.)

31. 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.

32. What is a Synonym? - A synonym is an alias for a table, view, sequence or program unit.

33. What is a Sequence? - A sequence generates a serial list of unique numbers for numerical columns of a database’s tables.

34. What is a Segment? - A segment is a set of extents allocated for a certain logical structure.

35. What is schema? - A schema is collection of database objects of a User.

36. 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.

37. 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.

38. What is a Private Synonyms? - A Private Synonyms can be accessed only by the owner.

39. What is Database Link? - A database link is a named object that describes a “path” from one database to another.

40. What is a Tablespace? - A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together

41. What is Rollback Segment? - A Database contains one or more Rollback Segments to temporarily store “undo” information.

42. 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.

43. 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 datablocks. Block size is specified in INIT.ORA file and can’t be changed latter.

44. 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 redolog files. Time stamp of database creation.

45. 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. 47.What is Index Cluster? - A Cluster with an index on the Cluster Key 48.When does a Transaction end? - When it is committed or Rollbacked.

46. What is the effect of setting the value “ALL_ROWS” for OPTIMIZER_GOAL parameter of the ALTER SESSION command? - What are the factors that affect OPTIMIZER in choosing an Optimization approach? - Answer The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.

47. What is the effect of setting the value “CHOOSE” for OPTIMIZER_GOAL, parameter of the ALTER SESSION Command? - The Optimizer chooses Cost_based approach and optimizes with the goal of best throughput if statistics for atleast one of the tables accessed by the SQL statement exist in the data dictionary. Otherwise the OPTIMIZER chooses RULE_based approach.

48. What is the function of Optimizer? - The goal of the optimizer is to choose the most efficient way to execute a SQL statement.

49. What is Execution Plan? - The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.

50. What are the different approaches used by Optimizer in choosing an execution plan? - Rule-based and Cost-based.

51. What does ROLLBACK do? - ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.

52. What is SAVE POINT? - For long transactions that contain many SQL statements, intermediate markers or savepoints can be declared which can be used to divide a transaction into smaller parts. This allows the option of later rolling back all work performed from the current point in the transaction to a declared savepoint within the transaction.

53. What are the values that can be specified for OPTIMIZER MODE Parameter? - COST and RULE.

54. What is COST-based approach to optimization? - Considering available access paths and determining the most efficient execution plan based on statistics in the data dictionary for the tables accessed by the statement and their associated clusters and indexes.

55. What does COMMIT do? - COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user sessions transactions that start only after transaction is committed.

56. What is RULE-based approach to optimization? - Choosing an executing plan based on the access paths available and the ranks of these access paths.

57. What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION Command? - CHOOSE,ALL_ROWS,FIRST_ROWS and RULE.

58. Define Transaction? - A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.

59. What is Read-Only Transaction? - A Read-Only transaction ensures that the results of each query executed in the transaction are consistent with respect to the same point in time.

60. What is a deadlock? - Explain . Two processes waiting to update the rows of a table which are locked by the other process then deadlock arises. In a database environment this will often happen because of not issuing proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically. These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.

61. What is a Schema? - The set of objects owned by user account is called the schema.

62. What is a cluster Key? - The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stored only once for multiple tables in the cluster.

63. What is Parallel Server? - Multiple instances accessing the same database (Only In Multi-CPU environments)

64. What are the basic element of Base configuration of an oracle Database? - It consists of one or more data files. one or more control files. two or more redo log files. The Database contains multiple users/schemas one or more rollback segments one or more tablespaces Data dictionary tables User objects (table, indexes, views etc.,) The server that access the database consists of SGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool) SMON (System MONito) PMON (Process MONitor) LGWR (LoG Write) DBWR (Data Base Write) ARCH (ARCHiver) CKPT (Check Point) RECO Dispatcher User Process with associated PGS

65. What is clusters? - Group of tables physically stored together because they share common columns and are often used together is called Cluster.

66. What is an Index? - How it is implemented in Oracle Database? - An index is a database structure used by the server to have direct access of a row in a table. An index is automatically created when a unique of primary key constraint clause is specified in create table command (Ver 7.0)

67. What is a Database instance? - Explain A database instance (Server) is a set of memory structure and background processes that access a set of database files. The process can be shared by all users. The memory structure that are used to store most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

68. What is the use of ANALYZE command? - To perform one of these function on an index, table, or cluster: - To collect statistics about object used by the optimizer and store them in the data dictionary. - To delete statistics about the object used by object from the data dictionary. - To validate the structure of the object.. - To identify migrated and chained rows off the table or cluster.

69. What is default tablespace? - The Tablespace to contain schema objects created without specifying a tablespace name.

70. What are the system resources that can be controlled through Profile? - The number of concurrent sessions the user can establish the CPU processing time available to the user’s session the CPU processing time available to a single call to ORACLE made by a SQL statement the amount of logical I/O available to the user’s session the amount of logical I/O available to a single call to ORACLE made by a SQL statement the allowed amount of idle time for the user’s session the allowed amount of connect time for the user’s session.

71. What is Tablespace Quota? - The collective amount of disk space available to the objects in a schema on a particular tablespace.

72. What are the different Levels of Auditing? - Statement Auditing, Privilege Auditing and Object Auditing.