Oracle interview Questions
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Oracle Concepts and Architecture
Database Structures
Qus. . What does a control file contains?
Ans: - Database name
- Names and locations of a database's files and redolog files.
- Time stamp of database creation.
Qus. . What is the use of control file?
Ans: 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.
Data Base Administration
Qus. . What is a database instance? Explain.
Ans: A database instance (Server) is a set of memory structure and
background processes that access a set of database files. The processes can be
shared by all of the users.
The memory structure that is used to store the most queried data from
database. This helps up to improve database performance by decreasing the
amount of I/O performed against data file.
Qus. . What is Parallel Server?
Ans: Multiple instances accessing the same database (only in multi-CPU
environments)
Qus. . What is a schema?
Ans: The set of objects owned by user account is called the schema.
Qus. . What is an index? How it is implemented in Oracle database?
Ans: 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
Qus. . What are clusters?
Ans: Group of tables physically stored together because they share common
columns and are often used together is called cluster.
Qus. . What is a cluster key?
Ans: 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.
Qus. . What is the basic element of base configuration of an Oracle
database?
Ans: 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
Qus. . What is a deadlock? Explain.
Ans: Two processes waiting to update the rows of a table, which are locked
by other processes then deadlock arises.
In a database environment this will often happen because of not issuing the
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.
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