a2zinterviews

25.	What do you understand by db file scattered read?
	Db file scattered read indicates a scatter read into multiple discontinuous locations. It generally indicates full table scan and that multiple blocks are being read into memory. Such reads are called scattered read calls, because the blocks are scattered throughout memory.
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26.	What do the db_file_sequential_read and db_file_scattered_read events indicate?
	The db_file_sequential_read event generally indicates index usage and shows an access by rowid while the db_file_scattered_read event indicates full table scan. A single block is read at one time in the db_file_sequential_read event while multiple blocks are read parallel in the db_file_scattered_read event.
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27.	Which trace file is used for performance tuning and why?
	User process trace file is used for performance tuning because it contains information about execution plan and resource consumption. This information can be used for performance tuning. These files are located in the directory specified in the BACKGROUND_DUMP_DIRECTORY parameter.
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28.	How can you monitor performance of the database pro–actively?
	Several tools, such as Oracle Enterprise Manager, and utilities from third party are available for monitoring database performance. However, all these tools or utilities depend on statistics gathered by Oracle, which are available through dynamic performance views.
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