Hosting the Transaction service outside of Sitecore
Even if you choose to host the transaction service outside of Sitecore in a separate IIS instance or some other form, you will still need to install the transaction package into Sitecore. Perform the steps in the previous task before attempting this one.
Create a separate IIS site & App Pool.
From one of the CM or CD servers:
Copy the contents of $\website\TransactionService\ into the root of the new website.
Configure the Transaction Service web.config file CommerceRunTimeConnectionString to point to your Dynamics AX for Retail Channel Database.