Alter table performance

Hi all, I have a question regarding performance. I need to alter several tables, changing columns from decimal(18,4) to decimal(19,8). Some of the tables have millions of rows. So, in your opinion/experience, what's the best way to do this?1) Using ALTER TABLE2) Creating a new one, updating with old value, delete old column and rename the new one? Keep in mind things like speed, log file size, etc. Thanks for any advice.Mauricio