In _The Firebird Book_ it states that changes to the column type are not
applied until the data is requested, and that a backup/restore should be
considered in order to reduce performance problems.

Would it be valid to select all items from the modified columns in order
to force the type conversion?

Once the data is converted, I assume it's permanent, and it's not the
case where the transformation takes place every time until a backup and
restore.

Rick DeBay