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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.
33. What is Data Block ?
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.
34. 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 cann't be changed latter.
35. What is Row Chaining ?
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.
36. What is an Extent ?
An Extent is a specific number of contiguous data blocks, obtained
in a single allocation, used to store a specific type of information.
37. What is a Segment ?
A segment is a set of extents allocated for a certain logical
structure.
38. What are the different type of Segments ?
Data Segment, Index Segment, Rollback Segment and Temporary Segment.
39. What is a Data Segment ?
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.
40. What is an Index Segment ?
Each Index has an Index segment that stores all of its data.
41. What is Rollback Segment ?
A Database contains one or more Rollback Segments to temporarily
store "undo" information.
42. What are the uses of Rollback Segment ?
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