a2zinterviews

13.	How long does the rollback segment hold data to maintain consistency?
	Rollback segment holds the previous version of data block until either its gets committed or the space is not available for reuse. If a session is reading specific block from rollback segment while the other session has committed the information, then more rollback space is required to maintain more rollback information. In that case, this specific block ages out of the rollback segment and the reading or selecting session gets an error.
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14.	What background process refreshes materialized views?
	The job queue processes refresh the materialized views.
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15.	What is the difference between a temporary tablespace and a permanent tablespace?
	A temporary tablespace provides temporary storage during the processing of database function, such as sorting; whereas a permanent tablespace is used to store permanent database objects, such as tables, partitions, indexes and clusters. You do not need to backup or restore a temporary tablespace.
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16.	What are the different types of memory structure available in Oracle?
	System Global Area (SGA) and Program Global Area (PGA) are the two types of memory structure available in Oracle.
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