First of all , new decentralized EWM is the same S/4HANA box which needs to be set (or flagged) as ‘EWM is Decentralized’ in IMG path SCM Extended warehouse management ->Extended warehouse management->Enable Decentralized EWM.
It is very important to note the SAP documentation on that IMG path which states “no other applications in SAP S/4HANA, such as PP, SD, or MM, will be used in the same client for the decentral warehouse-managed stock.” i.e ERP functionalities should not be carried in this decentralized EWM system.
Decentralized EWM on S/4HANA 1909 can be interfaced with ERP, either with ECC 6.0 Ehp 3 (or higher) or S/4HANA 1610 (or higher) as in below image. Refer SAP note 2871189 for more details.
There are some differences in transfer of master data from ERP to new decentralized EWM on S/4HANA as captured in below image. In present (or classic) decentralized EWM on NW or SCM , master data (Material , customer, vendor etc) is transferred to decentralized EWM through Core Interface (CIF), however ALE / IDOC or web service needs to be used to transfer material , batch , customer , vendor etc . However same CIF is to be used to transfer Packaging instruction.
SAP has provided an integration guide with note 2840129. There may be errors like in below image while trying to create customer (Business partner) in decentralized EWM on S/4HANA.
System is trying to create internal number range for the customer /BP as in above image . However, customers may prefer to have the same number also in decentralized EWM for customer or vendor number in ERP i.e the number range should be external in EWM. So, the number ranges may need to be fine tuned depending on the specific requirement .
As per the simplification in S/4HANA, customers / vendors are accessed through transaction BP (Business partner). Note that customers / vendors are still created in S/4HANA in same ERP tables( KNA1 for customer and LFA1 for vendor) along with BP table BUT000. So, the number ranges for the customer (/ vendor) and business partner need to be aligned for business partner grouping and customer (vendor) account group in EWM IMG menu paths as below
Cross application components->SAP Business partner->Basic settings->Number ranges and groupings->Define groupings and assign number ranges
Logistic general->Business partner->Customers->Control->Define and assign customer number ranges->Define Number Ranges for Customer Master
The above error is rectified by maintaining the number range set as external in decentralized EWM in above menu paths corresponding to customer / vendor number of ERP side. Number range for vendor also needs to be set up in same way. Logic for creation of business partner in decentralized EWM can be found in form DETERMINE_BP_GROUP of program SAPLVV02 .
Transaction data is transferred (bi-directional) through the same queued RFC in decentralized EWM on S/4HANA as shown above in 3rd image. Transaction document also looks the same as in embedded or classic decentralized EWM. Refer the below image for an inbound delivery in decentralized EWM on S/4HANA.
However, note that the functionalities in decentralized EWM on S/4HANA are not exactly the same as in embedded EWM or classic decentralized EWM 9.5 on NW or SCM. Refer note 2840129 for more details on differences.