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9.	What is the ORA-01555: snapshot too old error? How can it be avoided?
	The ORA-01555: snapshot too old error indicates that the query cannot find the snapshot it is looking for in the rollback segment. Rollback segment is designed to hold data blocks that are being changed. It is required to hold old snapshot until the transaction is committed. However, it holds the data until the space is required for other transactions.
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10.	How do you handle ORA – 01403: no data found error?
	You can handle ORA- 01403: no data found error by terminating the processing for the SELECT statement.
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11.	Name three advisory statistics you can collect?
	The three advisory statistics that can be collected are Buffer Cache Advice Segment Level Statistics and Timed Statistics
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12.	What are different types of locks?
	There are two different types of locks, which are given as follows: System locks – Held for a very brief period of time and controlled by Oracle. User locks – Created and managed using dbms_lock package. Different types of user locks are given as follows: The UL lock – Defined with the dbms_lock package. The TX lock – Acquired once for every transaction. It is a row transaction lock. The TM lock – Acquired once for each object, which is being changed. It is a DML lock. The IDI column identifies the object being modified.
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