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33.	How many rows in a table chained?
	The information about chained rows is available in either the chain_cnt column or the dba_tables, all_tables or user_tables view. However, this information can be out dated. You need to analyze the table to get the correct information in these views.
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34.	How does row migration affect performance?
	In case of full table scan, the optimizer ignores rowid of individual migrated rows. Therefore, full table scans are not affected by row migration. Index reads causes additional I/O's on migrated rows. In case of index read, rowids cannot be ignored. In such a case, the index scan will need to read at least two locations for a migrated row as compared to a single read for a non migrated row. Therefore, index scans are adversely affected by row migration.
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35.	How can you avoid chained or migrated rows?
	You can set PCTFREE to a higher value to avoid migrated rows; whereas, to avoid chained rows, you need to set appropriate size for data block and design the tables appropriately. In addition, you can reorganize tables to reduce number of migrated or chained rows. The ALTER TABLE --- MOVE statement is used to re-organize a table.
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36.	How do you ensure that control file is safe considering the importance of it?
	Multiplexing is used to ensure availability of the control file. It means creating multiple copies of the control file. Ideally, you should keep those copies in different physical locations so that in case of media failure, you have at least one copy of control file that can be used.
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