SalesCart has nothing special to do with the connection string or the ability to read/write to the database. It simply reads the connection string out of the file....it either works or it doesn't work.
If it doesn't work, its not a problem in SalesCart, its a problem with the connection string, database, database permissions, etc. 90% of all SalesCart issues are the issue your having....bad database connection or database permissions are bad...thats why many folks host with ComCity and avoid these issues. The only other way to avoid it is a shopping cart service, where this "task" is taken away from you.
Once again-->You CANT use the
same DSN. The DSN is on the server...you have no access to it accept via a connection string. The DSN on your local computer may have the same name...but they are completely different.
If the connection is on again off again...you have an issue with your ISP simple as that....just if you website worked some of the time and other times it did not. And an entirely different website with a different database is also not relevent.