Once an audit trail has been started for a table, the table should not be altered. If you must alter the table, do the following. Copy the table to a backup medium. Use DROP AUDIT to remove the audit trail. Delete the audit-trail file. Alter the table. Again, copy the table to a backup medium. Finally, use CREATE AUDIT to start a new audit trail. The first backup is needed to restore the table if a failure occurs while the table is being altered (a lengthy, disk-intensive procedure if the table is large). The second backup is required because, if the table has to be recovered later, the new audit trail must be applied against a backup that has the same layout of columns.