To answer this question, you need to understand the concept of check constraints in Oracle.

Check constraints in Oracle allow you to define a condition that must be true for each row in a table. This condition is specified as an expression, and it can reference multiple columns in the table. The purpose of a check constraint is to ensure that the data in the table meets certain criteria.

Let's go through each option to understand why it is correct or incorrect:

Option A) Values must be obtained from a lookup table. This option is incorrect because check constraints in Oracle do not require values to be obtained from a lookup table. The values can be any valid expression that evaluates to true or false.

Option B) Values must be part of a fixed set defined by create or alter table. This option is correct. Check constraints in Oracle can be used to enforce that the values in a column must be part of a fixed set defined by the create or alter table statement. This means that the values must be explicitly specified and cannot be any arbitrary values.

Option C) Values must include reserved words, such as SYSDATE and USER. This option is incorrect. Check constraints in Oracle do not require values to include reserved words. The values can be any valid expression that evaluates to true or false.

Option D) The column cannot contain a NULL value. This option is incorrect. Check constraints in Oracle can allow NULL values in a column. Whether or not NULL values are allowed is determined by the NULL or NOT NULL constraint, not the check constraint.

The correct answer is B) Values must be part of a fixed set defined by create or alter table. This option is correct because it accurately describes one of the limitations on check constraints in Oracle.

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• Wrong explanation

To answer this question, you need to understand transaction control in database management systems.

Option A) Lock - This option is correct because locks are used to prevent more than one user from updating data in a table simultaneously. Locks are acquired on the table or specific rows and are released after the transaction is complete.

Option B) Commit - This option is incorrect because the commit operation is used to permanently save the changes made during a transaction. It does not prevent multiple users from updating data simultaneously.

Option C) Rollback - This option is incorrect because the rollback operation is used to undo the changes made during a transaction and restore the database to its previous state. It does not prevent multiple users from updating data simultaneously.

Option D) Savepoint - This option is incorrect because savepoints are used to mark a specific point within a transaction to which it can be rolled back. It does not prevent multiple users from updating data simultaneously.

The correct answer is A) Lock. This option is correct because locks are used to prevent more than one user from updating data in a table simultaneously.

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• Wrong explanation

To answer this question, you need to understand what ASM stands for and its purpose.

ASM stands for Automatic Storage Management. It is a feature provided by Oracle Database that combines the functionalities of a volume manager and a file system.

Option A) an integrated file system only - This option is incorrect because ASM is not just an integrated file system. It also includes volume management capabilities.

Option B) A mirroring technology only - This option is incorrect because ASM is not solely a mirroring technology. While it does provide mirroring capabilities, it also includes volume management and file system functionalities.

Option C) an integrated file system with a volume manager - This option is correct. ASM combines the functionalities of a volume manager and a file system, allowing for efficient management and allocation of storage resources.

Option D) A Volume manager only - This option is incorrect because ASM is not only a volume manager. It also includes file system functionalities.

The correct answer is C) an integrated file system with a volume manager. This option is correct because it accurately describes the capabilities of ASM.

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• Wrong explanation