COMMON_QUEST

[sher...@gmail.com]

1. What is Log Switch? - The point at which ORACLE ends writing to one
online redo log file and begins writing to another is called a log
switch.
2. What is On-line Redo Log? - The On-line Redo Log is a set of tow 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.
3. Which parameter specified in the DEFAULT STORAGE clause of CREATE
TABLESPACE cannot be altered after creating the tablespace? - 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.
4. What are the steps involved in Database Startup? - Start an
instance, Mount the Database and Open the Database.
5. What are the steps involved in Instance Recovery? - 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.
6. Can Full Backup be performed when the database is open? - No.
7. What are the different modes of mounting a Database with the
Parallel Server? - 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 a database
is started in parallel mode, other instances that are started in
parallel mode can also mount the database.
8. What are the advantages of operating a database in ARCHIVELOG mode
over operating it in NO ARCHIVELOG mode? - Complete database recovery
from disk failure is possible only in ARCHIVELOG mode. Online database
backup is possible only in ARCHIVELOG mode.
9. What are the steps involved in Database Shutdown? - Close the
Database, Dismount the Database and Shutdown the Instance.
10. What is Archived Redo Log? - Archived Redo Log consists of Redo
Log files that have archived before being reused.
11. What is Restricted Mode of Instance Startup? - An instance can be
started in (or later altered to be in) restricted mode so that when
the database is open connections are limited only to those whose user
accounts have been granted the RESTRICTED SESSION system privilege.
12. What is Partial Backup? - A Partial Backup is any operating system
backup short of a full backup, taken while the database is open or
shut down.
13. What is Mirrored on-line Redo Log? - A mirrored on-line redo log
consists of copies of on-line redo log files physically located on
separate disks, changes made to one member of the group are made to
all members.
14. What is Full Backup? - A full backup is an operating system backup
of all data files, on- line redo log files and control file that
constitute ORACLE database and the parameter.
15. Can a View based on another View? - Yes.
16. Can a Tablespace hold objects from different Schemes? - Yes.
17. Can objects of the same Schema reside in different tablespaces? -
Yes.
18. 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.
19. Do View contain Data? - Views do not contain or store data.
20. 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.
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.
1. What does ROLLBACK do? - ROLLBACK retracts any of the changes
resulting from the SQL statements in the transaction.
2. 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.
3. What are the values that can be specified for OPTIMIZER MODE
Parameter? - COST and RULE.
4. 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.
5. 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.
6. What is RULE-based approach to optimization? - Choosing an
executing plan based on the access paths available and the ranks of
these access paths.
7. What are the values that can be specified for OPTIMIZER_GOAL
parameter of the ALTER SESSION Command? - CHOOSE,ALL_ROWS,FIRST_ROWS
and RULE.
8. Define Transaction? - A Transaction is a logical unit of work that
comprises one or more SQL statements executed by a single user.
9. 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.
10. 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.
11. What is a Schema? - The set of objects owned by user account is
called the schema.
12. 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.
13. What is Parallel Server? - Multiple instances accessing the same
database (Only In Multi-CPU environments)
14. 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
15. What is clusters? - Group of tables physically stored together
because they share common columns and are often used together is
called Cluster.
16. 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)
17. 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.
18. 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.
19. What is default tablespace? - The Tablespace to contain schema
objects created without specifying a tablespace name.
20. 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.
21. What is Tablespace Quota? - The collective amount of disk space
available to the objects in a schema on a particular tablespace.
22. What are the different Levels of Auditing? - Statement Auditing,
Privilege Auditing and Object Auditing.
23. What is Statement Auditing? - Statement auditing is the auditing
of the powerful system privileges without regard to specifically named
objects
24. What are the database administrators utilities available? - SQL *
DBA - This allows DBA to monitor and control an ORACLE database. SQL *
Loader - It loads data from standard operating system files (Flat
files) into ORACLE database tables. Export (EXP) and Import (imp)
utilities allow you to move existing data in ORACLE format to and from
ORACLE database.
25. How can you enable automatic archiving? - Shut the database Backup
the database Modify/Include LOG_ARCHIVE_START_TRUE in init.ora file.
Start up the database.
26. What are roles? - How can we implement roles? - Roles are the
easiest way to grant and manage common privileges needed by different
groups of database users. Creating roles and assigning provides to
roles. Assign each role to group of users. This will simplify the job
of assigning privileges to individual users.
27. What are Roles? - Roles are named groups of related privileges
that are granted to users or other roles.
28. What are the use of Roles? - REDUCED GRANTING OF PRIVILEGES -
Rather than explicitly granting the same set of privileges to many
users a database administrator can grant the privileges for a group of
related users granted to a role and then grant only the role to each
member of the group. DYNAMIC PRIVILEGE MANAGEMENT - When the
privileges of a group must change, only the privileges of the role
need to be modified. The security domains of all users granted the
group’s role automatically reflect the changes made to the role.
SELECTIVE AVAILABILITY OF PRIVILEGES - The roles granted to a user can
be selectively enable (available for use) or disabled (not available
for use). This allows specific control of a user’s privileges in any
given situation. APPLICATION AWARENESS - A database application can be
designed to automatically enable and disable selective roles when a
user attempts to use the application.
29. What is Privilege Auditing? - Privilege auditing is the auditing
of the use of powerful system privileges without regard to
specifically named objects.
30. What is Object Auditing? - Object auditing is the auditing of
accesses to specific schema objects without regard to user.
31. What is Auditing? - Monitoring of user access to aid in the
investigation of database use.
32. What are the responsibilities of a Database Administrator?
o Installing and upgrading the Oracle Server and application tools.
o Allocating system storage and planning future storage requirements
for the database system.
o Managing primary database structures (tablespaces)
o Managing primary objects (table, views, indexes)
o Enrolling users and maintaining system security.
o Ensuring compliance with Oracle license agreement
o Controlling and monitoring user access to the database.
o Monitoring and optimizing the performance of the database.
o Planning for backup and recovery of database information.
o Maintain archived data on tape
o Backing up and restoring the database.
o Contacting Oracle Corporation for technical support.
33. What is a trace file and how is it created? - Each server and
background process can write an associated trace file. When an
internal error is detected by a process or user process, it dumps
information about the error to its trace. This can be used for tuning
the database.
34. What is a profile? - Each database user is assigned a Profile that
specifies limitations on various system resources available to the
user.
35. How will you enforce security using stored procedures? - Don’t
grant user access directly to tables within the application. Instead
grant the ability to access the procedures that access the tables.
When procedure executed it will execute the privilege of procedures
owner. Users cannot access tables except via the procedure.


Regards,

Mohammed sheriff.s