19.12 Using Data Masking with LONG Columns

When data masking script generation completes, an impact report appears. If the masking definition has tables with columns of data type LONG, the following warning message is displayed in the impact report:

The table <table_name> has a LONG column. Data Masking uses "in-place" UPDATE 
to mask tables with LONG columns. This will generate undo information and the
original data will be available in the undo tablespaces during the undo 
retention period. You should purge undo information after masking the data. 
Any orphan rows in this table will not be masked.