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continuation for the previous paper.
Posted Date: 28 Feb 2008 Resource Type: Articles/Knowledge Sharing Category: General
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Posted By: Deepu Member Level: Diamond
Rating:  Points: 5
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41. What is a Tablespace?
A database is divided into Logical Storage Unit called tablespaces.
A tablespace is used to grouped related logical structures together
42. What is Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily
store "undo" information.
43. 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.
44. 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.
45. 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.
46.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.
49. 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.
50. 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.
51. What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to
execute a SQL statement.
52. What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a
statement is called an execution plan.
53. What are the different approaches used by Optimizer in choosing
an execution plan ?
Rule-based and Cost-based.
54. What does ROLLBACK do ?
ROLLBACK retracts any of the changes resulting from the SQL
statements in the transaction.
55. 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.
56. What are the values that can be specified for OPTIMIZER MODE
Parameter ?
COST and RULE.
57. 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.
58. 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.
59. What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and
the ranks of these access paths.
60. What are the values that can be specified for OPTIMIZER_GOAL
parameter of the ALTER SESSION Command ?
31. What is a Synonym ?
A synonym is an alias for a table, view, sequence or program unit.
32. What is a Sequence ?
A sequence generates a serial list of unique numbers for numerical
columns of a database's tables.
33. What is a Segment ?
A segment is a set of extents allocated for a certain logical
structure.
34. What is schema?
A schema is collection of database objects of a User.
35. 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.
36. 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.
37. What is a Private Synonyms ?
A Private Synonyms can be accessed only by the owner.
40. What is Database Link ?
A database link is a named object that describes a "path" from one
database to another.
41. What is a Tablespace?
A database is divided into Logical Storage Unit called tablespaces.
A tablespace is used to grouped related logical structures together
42. What is Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily
store "undo" information.
43. 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.
44. 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.
45. 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.
46.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.
49. 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.
50. 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.
51. What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to
execute a SQL statement.
52. What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a
statement is called an execution plan.
53. What are the different approaches used by Optimizer in choosing
an execution plan ?
Rule-based and Cost-based.
54. What does ROLLBACK do ?
ROLLBACK retracts any of the changes resulting from the SQL
statements in the transaction.
55. 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.
56. What are the values that can be specified for OPTIMIZER MODE
Parameter ?
COST and RULE.
57. 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.
58. 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.
59. What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and
the ranks of these access paths.
60. What are the values that can be specified for OPTIMIZER_GOAL
parameter of the ALTER SESSION Command ?
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