a2zinterviews

17.	What is System Change Number (SCN)?
	SCN is an ID that Oracle generates for every transaction. It is recorded with the corresponding change in a redo entry.
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18.	Why do you mean PGA?
	PGA is a memory area used by Oracle database. It is required to store session specific information.
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19.	What is a listener process?
	The listener or Transparent Network Substrate (TNS) listener is a server process that provides network connectivity to the Oracle database. The listener is configured to listen for connection requests on a specified port on the database server. When an incoming request is received on the port, the listener attempts to resolve the request and forward the connection information to the appropriate database instance.
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20.	What is the physical structure of the disk resources in Oracle?
	Following is the physical structure of the disk resources in Oracle. Control files – stores the status of the physical structure of the database. It contains different types of information, such as archive log history, data files records, redo threads, log records, and database name. Data files – Refers to the physical files of the operating system that store the data of all logical structures in the database. Redo log files – Refers to the files, which log a history of all changes made to the database.
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