Explanation:

6: After the DBA issues the following command all undo segments in the smu_tbsl tablespace will have v$rollstat.status = 'PENDING OFFLINE' until all existing transactions have been committed or rolled back. All new transactions will use smu_tbs2.
Incorrect Answers:
1: Oracle will not dynamically balance a new rollback usage request across segments in both smu_tbsl and smu_tbs2. All new transactions will use smu_tbs2. Running transactions in the smu_tb1 tablespace will have v$rollstat.status = 'PENDING OFFLINE'.
2: Existing sessions with active transactions will not get an error: they will have v$rollstat.status = 'PENDING OFFLINE' until all existing transactions have been committed or rolled back.
3: The ALTER SYSTEM command will fail.
5: The DBA have not to dynamically change undo_managment = MANUAL.
Reference:
OCP Oracle9i Database: New Features for Administrators, Daniel Benjamin, p. 160-164
Chapter 3: Manageability Enhancements
Oracle 9i New Features, Robert Freeman, p. 19-25
Chapter 1: Oracle9i Database Administration and Management Features

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