Author has been leading the Master Data maintenance and distribution for several years. Master Data is so much integrated with other components that accuracy and sync of MD are very critical for successful SAP Implementations.
Please see Process Diagram presented here, and I hope this will give you a simple and clear understandings for SAP professionals.
1. ERP to SCM, EWM
CIF (Core Interface) distributes major Master Data objects such as Materials, Plant, Customers (location Master in SCM), Vendors (location Master in SCM), Scheduling Agreement (External Procurement Relationship), MRP areas. Depending on the situation of company, CIF can run in either Batch mode or Immediate mode. Multiple CIF jobs can be set up to send to many destinations as described in diagram. Generation of CIF (CFM1 for instance) and Activation of CIF (CFM2) are major steps in CIF processing.
2. ERP to CRM
Materials are distributed from ERP to CRM via BDOC.
3. CRM to ERP, SCM, EWM
BP Master Data (Customers and Vendors) are distributed from CRM to ERP via BDPC. At the same time, these BP master data are sent to SCM and EWM via IDOC. Distribution is taking place immediately. Transaction SMW01 is available to monitor queue record in CRM.
4. SCM to EWM
Pack Specs are created in SCM and these are also distributed to EWM via RFC queue. Queue records are monitored by SMQ1 and SMQ2 command.
XI primarily governs all external inputs from Legacy or External systems. Each record can be monitored XI command SXMB_MONI, and the records can be reprocessed when error happens.