While WebSphere Commerce (WC) can do basic order management very well, you may have some requirements that will push you to a third party order management system. One example would be a cross-channel call center, like the one in Sterling Order Management, another solution in the Smarter Commerce portfolio. If you have the developer edition of WC 7, feature pack 4 you can configure the base Madisons store for the external order management function by following these instructions: link here.
Now, if you create other sites from the same asset store (a peer to the Madisons store) the only thing you really have to do is Step 12 from the same link above:
UPDATE STORE SET INVENTORYSYSTEM=-5 WHERE STORE_ID IN (SELECT STOREENT_ID FROM STOREENT WHERE IDENTIFIER='Store_Identifier' );
This sets the inventory system to a third party one, that is what the -5 value represents. Once that is complete you need to make sure the INVCNFREL table either has entries for your store id or make sure the STORE_ID is NULL for the items you want handled by the external system. Being NULL means any stores set to “-5″ will use the external management system. Here are a couple of records from that table:
select * from INVCNFREL;