Going to live operation on the new system is not a single event, but rather a phased series of events. Initial data values are loaded into the new system just before and during initial live operation. Not all modules are implemented at the same time, though certain sets of modules start together, like the Order Entry set including Accounts Receivable, Inventory Accounting and Sales Analysis. There may be a period of overlap, with some functions still on the old system and some on the new. As each function begins live operation on the new system, that function ends on the old. The old system can be shut down when all modules are live on the new system and any desired history is brought over to the new system. Fine-tuning and adjustments take place throughout the phases.