Types of Changes
Additive Schema Changes make the following types of schema changes to support the new release. These changes do not adversely affect data integrity or database normalization:
Creating new tables.
Adding columns to an existing table. The column must either be specified as null, or if the column is not null, it must have a specified default value.
Increasing column sizes for numeric or varchar columns. The column must not be the basis for a picklist. Also, the resultant cumulative row size must not be larger than the data page size.
Revising a not-null column to null.
Revising data type from char to varchar.