A recent client of mine was in the habit of naming Cognos data source connections after the environment they were connecting to, as was the custom of the underlying Oracle TNS names. So a connection to a DEV, TEST or QA source would have some notation of this in its name, such as MyConnection_DEV. This worked fine until it came time to migrate the project from one environment to another, and then this data source connection configuration turned into a real headache.
Because each environment had its own unique data source connection name, it was impossible to simply export Cognos packages from one level and import into another. Modifying FM data models and republishing them was necessary, which was a lot more work than it should have been. One developer even complained that he felt like he had to start each project over every time he migrated it. I think that is a good way to look at a Cognos data source connection – a starting point. Modifying this starting point (by which I mean its name, not its attributes) means you are in a sense starting over. A better approach is to maintain a standard name across your DEV/QA/PROD environments so that you do not have so much extra work every time you migrate. With this name constant, you can set your attributes in each environment freely to connect to whichever database you desire. This prevents having to republish packages or remap data connections at every turn.