SOAP Web Services List Operations
Within a single SOAP request, only one operation can be performed. For example, one add, one addList or one delete. However, a single list operation (addList, updateList, upsertList, deleteList, getList, and initializeList) lets you work with multiple record types. For example, with a single addList operation you can add 3 customers, 4 opportunities, and 1 contact.
List operations process records in the order in which the records are submitted. For example, an addList operation will add all records in the order they appear in the list.