Can we change the data type and size in a table when data is there and when data is not there?

Question

Why should I not commit after every record when updating a large table Committing after every record does not hurt but its much efficient to commit after a batch of records like 5000 - 7000.

Answer 1

When there is data we can increase the size, we can not decrease the size but we cannot change the data type.
Yes we can change the data type and size when there is no data