I am migrating ssis 2005 packages to ssis 2012.Just wondering what is the difference
1) If I manually attach the 2005 packages to ssis 2012 project and modified all the objects according the new environment
2) Using the upgradation Wizard to upgrade all packages from 2005 to 2012
You can do either way. if you do it manually the wizard will pop up when you open the migrated package for the first time in SQL Server Data Tools, which is the replacement for BI Development Studio. In any case you might need to some manual steps. One of the main things you have to decide is what kind of deployment model you want to adopt since SSIS 2012 has two: package and project deployment models. There are a few documents released by Microsoft that can help you through the process. For example, this short document covers the most important aspects to perform a safe migration:
https://msdn.microsoft.com/en-us/library/hh667275.aspx
The good thing about the wizard is that will validate the package before the upgrade and make sure that it can run in 2012; in most cases the migration is possible bar a few exceptions like packages using third party components that cannot be upgraded.
