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Technicle questions of Oracle.
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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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.
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.
8. What are the steps involved in Database Shutdown ?
Close the Database, Dismount the Database and Shutdown the Instance.
9. What is Archived Redo Log ?
Archived Redo Log consists of Redo Log files that have archived
before being reused.
10. 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.
11. 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.
12. 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.
13. 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.
14. Can a View based on another View ?
Yes.
15. Can a Tablespace hold objects from different Schemes ?
Yes.
16. Can objects of the same Schema reside in different tablespaces.?
Yes.
17. 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.
18. Do View contain Data ?
Views do not contain or store data.
19. 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.
20. What are the type of Synonyms?
There are two types of Synonyms Private and Public
21. 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.
22. What is an Index Segment ?
Each Index has an Index segment that stores all of its data.
23. 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
24. What are the different type of Segments ?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.
25. What are Clusters ?
Clusters are groups of one or more tables physically stores together
to share common columns and are often used together.
26. What is an Integrity Constrains ?
An integrity constraint is a declarative way to define a business
rule for a column of a table.
27. 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.
28. 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.
29. 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.)
30. 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.
Top
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.
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