Oracle interview Questions
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Oracle Concepts and Architecture
Database Structures
Qus. . What is a segment?
Ans: A segment is a set of extents allocated for a certain logical
structure.
Qus. . What are the different types of segments?
Ans: Data segment, index segment, rollback segment and temporary segment.
Qus. . What is a data segment?
Ans: Each non-clustered table has a data segment. All of the table's data
is stored in the extents of its data segment. Each cluster has a data segment.
The data of every table in the cluster is stored in the cluster's data
segment.
Qus. . What is an index segment?
Ans: Each index has an index segment that stores all of its data.
Qus. . What is rollback segment?
Ans: A database contains one or more rollback segments to temporarily store
"undo" information.
Qus. . What are the uses of rollback segment?
Ans: To generate read-consistent database information during database
recovery and to rollback uncommitted transactions by the users.
Qus. . What is a temporary segment?
Ans: Temporary segments are created by Oracle when a SQL statement needs a
temporary work area to complete execution. When the statement finishes
execution, the temporary segment extents are released to the system for future
use.
Qus. . What is a datafile?
Ans: Every Oracle database has one or more physical data files. A
database's data files contain all the database data. The data of logical
database structures such as tables and indexes is physically stored in the
data files allocated for a database.
Qus. . What are the characteristics of data files?
Ans: 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.
Qus. . What is a redo log?
Ans: The set of redo log files for a database is collectively known as the
database redo log.
Qus. . What is the function of redo log?
Ans: The primary function of the redo log is to record all changes made to
data.
Qus. . What is the use of redo log information?
Ans: The information in a redo log file is used only to recover the
database from a system or media failure prevents database data from being
written to a database's data files.
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