Oracle interview Questions
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Oracle Concepts and Architecture
Database Structures
Qus. . What is index cluster?
Ans: A cluster with an index on the cluster key.
Qus. . What is hash cluster?
Ans: 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.
Qus. . When can hash cluster used?
Ans: Hash clusters are better choice when a table is often queried with
equality queries. For such queries the specified cluster key value is hashed.
The resulting hash key value points directly to the area on disk that stores
the specified rows.
Qus. . What is database link?
Ans: A database link is a named object that describes a "path" from one
database to another.
Qus. . What are the types of database links?
Ans: Private database link, public database link & network database link.
Qus. . What is private database link?
Ans: Private database link is created on behalf of a specific user. A
private database link can be used only when the owner of the link specifies a
global object name in a SQL statement or in the definition of the owner's
views or procedures.
Qus. . What is public database link?
Ans: Public database link is created for the special user group PUBLIC. A
public database link can be used when any user in the associated database
specifies a global object name in a SQL statement or object definition.
Qus. . What is network database link?
Ans: Network database link is created and managed by a network domain
service. A network database link can be used when any user of any database in
the network specifies a global object name in a SQL statement or object
definition.
Qus. . What is data block?
Ans: Oracle database's data is stored in data blocks. One data block
corresponds to a specific number of bytes of physical database space on disk.
Qus. . How to define data block size?
Ans: 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 data blocks. Block size is specified in init.ora file and cannot be
changed latter.
Qus. . What is row chaining?
Ans: In circumstances, all of the data for a row in a table may not be able
to fit in the same data block. When this occurs, the data for the row is
stored in a chain of data block (one or more) reserved for that segment.
Qus. . What is an extent?
Ans: An extent is a specific number of contiguous data blocks, obtained in
a single allocation and used to store a specific type of information.
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