Solution : https://service.sap.com/sap/support/notes/653645 (SAP Service marketplace login required)
Key words : 
prerequisites performance problems solution notes, bw initial data transfer, terms bw extraction reason, symptom bad performance, transaction processing
Related Notes : 
       
| 692195 | FAQ: Sales Analytics and CRM-BW data Extraction | 
| 641872 | Bad performance during the reading of the product data | 
| 636732 | SRCICREL: Missing index and incorrect buffering | 
| 636457 | NREL_GET_NEIGHBOURHOOD: Too many DB accesses despite filter | 
| 636389 | Bad performance during the document flow reading | 
| 636032 | Bad performance during the reading of transactions | 
| 634263 | Selects with FOR ALL ENTRIES | 
| 631846 | Poor performance when reading dates | 
| 610347 | Performance: Filling the item number | 
| 607758 | Poor performance when reading documents | 
| 602108 | Performance improvements in the partner processing | 
| 602078 | Performance problems during BDoc message processing | 
| 601319 | BW extractors, determine performance for document flow | 
| 597678 | Performance decreases with the number of processed documents | 
| 593659 | BW, termination of initial area load SALES, conditions | 
| 591276 | CRM 3.+: Performance in the CRM order | 
| 590557 | BW, termination with initial load of business transactions | 
| 572892 | Buffer refresh for partner checks during initialization | 
| 572695 | BW, initialization of internal table during initial upload | 
| 569673 | Performance: Too many date conversions | 
| 563141 | Performance: too many database accesses to CRMD_SCHEDLIN | 
| 557889 | Performance optimization DatesSet | 
| 557807 | Improvement performance BW extraction SALES part 2 | 
| 544384 | Performance: document flow | 
| 536414 | CRM 3.0/3.1 SAP Composite Note: Middleware reorganization | 
| 527409 | BW extraction activity, opportunity performance improvement | 
| 521299 | 1O extractor: Extraction from CRM to BW is too slow | 
| 505635 | BW extraction SALES, performance improvement | 
| 447622 | Poor performance when reading document flow | 
| 445791 | Bad performance when the document flow is read |