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Which statement is true regarding online redefinition for the migration of BasicFile LOBs to SecureFile LOBs?

It cannot be done in parallel.

It can be done at the table level or partition level.

It does not require additional storage because the operation is done online.

Local and global indexes are maintained automatically during the operation.

Refer to here
Compatibility and Upgrading
All features described in this document are enabled with compatibility set to or higher. There is no
downgrade capability after is set.
If you want to upgrade BasicFiles LOBs to SecureFiles LOBs, you must use typical methods for upgrading data
(CTAS/ITAS, online redefinition, export/import, column to column copy, or using a view and a new column).
Most of these solutions require twice the disk space used by the data in the input LOB column. However,
partitioning and taking these actions on a partition-by-partition basis lowers the disk space requirements.
Migrating Columns from BasicFiles LOBs to SecureFiles LOBs
The method of migrating LOBs columns is presented in this section.
Preventing Generation of REDO Space when Migrating to SecureFiles LOBsGeneration of redo space can cause performance problems during the process of migrating BasicFiles LOB
columns. Redo changes for the table are logged during the migration process only if the table has LOGGING
Redo changes for the column being converted from BasicFiles LOB to SecureFiles LOB are logged only if the
storage characteristics of the SecureFiles LOB column indicate LOGGING. The logging setting (LOGGING or
NOLOGGING) for the LOB column is inherited from the tablespace in which the LOB is created.
To prevent generation of redo space during migration make sure that you specify the NOLOGGING storage
parameter for the new SecureFiles LOB column(s). You can turn LOGGING on once your migration is
Online Redefinition for BasicFiles LOBs
Online redefinition is the only recommended method for migration of BasicFiles LOBs to SecureFiles LOBs. It
can be done at the table or partition level.
Online Redefinition Advantages
No requirement to take the table or partition offline Can be done in parallel
Online Redefinition Disadvantages
Additional storage equal to the entire table or partition and all LOB segments must be available Global indexes
must be rebuilt

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