On Feb 16, 2011, at 7:19 PM, Michael Schrag wrote:
>> 
>> Be aware that it might cause problems if you deploy a new version that do 
>> database schema changes. For example, if you change the constraint on a 
>> column so that it cannot accept NULL anymore and the older version of your 
>> app don't have that change in its model, current sessions in the older 
>> version will get an JDBC exception when they try to put NULL in the column 
>> where the constraint was changed.
>> 
>> Many other database changes will also cause problems.  If you need to update 
>> the schema, you pretty much have to schedule a service outage.
> You just have to be a lot more careful and have stricter rules about what 
> kind of changes you allow. For instance, you can't add new not null 
> constraints unless you have default values (at least initially).
>> 

OK, that was a rather large brush for me to tar it with.  Removing or renaming 
columns is a problem that  I don't think you can get around.  Adding nullable 
columns is OK.


Chuck

-- 
Chuck Hill             Senior Consultant / VP Development

Practical WebObjects - for developers who want to increase their overall 
knowledge of WebObjects or who are trying to solve specific problems.    
http://www.global-village.net/products/practical_webobjects







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