Created by Jerry Wang, last modified on Oct 06, 2014
variant 1: 异步update
variant 2： 同步update
variant 3
根据ABAP help 对关键字SET UPDATE TASK LOCAL的说明(The local update function performs a synchronous update after the COMMIT WORK statement, independently of the addition AND WAIT), variant 3还是属于同步update:( 总的gross time仍然为3秒)