From DB explorer of Toad for DB2 version 4.5, user right clicks on a database object and selects Migrate option to migrate table changes between environments. The migration script generates drop & recreate and export/import if option "preserve data" is selected. Performing the exact same steps from Toad for DB2 version 4.0 will generate 'Alter table ... Add Column' commands.
User is able to achieve similar functionality by selecting 'Compare' option of Toad for DB2 version 4.5
An Enhancement Request is submitted so migration would have a single Alter statement with multiple 'Add Columns', rather than have multiple alter statements:
alter tab1 add column col1 char(2)
add column col2 int
add column col3 timestamp;
alter tab1 add column col1 char(2);
alter tab1 add column col2 int;
alter tab1 add column col3 timestamp;
Enhancement request ST 66050 has been submitted to Development for consideration in a future release of Toad for DB2.
To generate Alter table statement instead of Export/Import, use Compare Object option instead of Migrate in Toad for DB2 version 4.5