Explanation:
The default scope of changes made by using the SET clause of the ALTER SYSTEM statement is only MEMORY scope. The MEMORY scope only makes changes in memory for the current instance and not the SPFILE; it does not persist.
Incorrect Answers:
2: The SPFILE is not a default scope of changes made by using the SET clause of the ALTER SYSTEM statement. It makes changes only in the SPFILE and not in the instance.
3: The ALTER SYSTEM command does not change the init<SID>.ora file.
4: Only MEMORY scope is updated by default.
5: The init<SID>.ora file is not updated by the ALTER SYSTEM command.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 80-83
Chapter 2: Availability Enhancements
Oracle 9i New Features, Robert Freeman, p. 32-37
Chapter 1: Oracle9i Database Administration and Management Features

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