在SAP开发我的项目，这两个概念开发人员根本都晓得。然而没有去比照其性能区别。
首先，咱们遍及一下原理。
Workarea: 相当于在内存堆栈外面开拓了一块内存。
Field Symbols:相当于存了内存的地址。所以实际上是不占用内存的。相当于C语言的曾经被解除援用的指针。
所以咱们进行一项性能测试：
1.比照单纯Loop的性能，不进行数据批改。
REPORT zloop_performance_test.DATA : v_start_time TYPE timestampl, v_end_time TYPE timestampl, v_diff_w TYPE p DECIMALS 5.TYPES : BEGIN OF ty_vbrp, vbeln TYPE vbrp-vbeln, END OF ty_vbrp.DATA : lt_vbrp TYPE STANDARD TABLE OF ty_vbrp, ls_vbrp TYPE ty_vbrp.FIELD-SYMBOLS : <fs_vbrp> TYPE ty_vbrp.PARAMETERS p_count TYPE n LENGTH 6.* Start of selectionSTART-OF-SELECTION.* Get billing item data SELECT vbeln FROM vbap INTO TABLE lt_vbrp UP TO p_count ROWS.END-OF-SELECTION.* 1 . Loop with work area GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp INTO ls_vbrp. ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE :/(30) 'Loop with Work area', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.* 2 . Loop with work area inline declaration GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp INTO DATA(ls_vbrp_inline). ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE:/(30) 'Loop with Inline Work area', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.* 3 . Loop with Field symbol GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp ASSIGNING <fs_vbrp>. ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE:/(30) 'Loop with Field Symbol', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.* 4 . Loop with Field symbol inline declaration GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp ASSIGNING FIELD-SYMBOL(<fs_vbrp_inline>). ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE:/(30) 'Loop with Inline Field Symbol', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.2.比照loop，并将数据批改如上面的代码：
REPORT zloop_performance_test.DATA : v_start_time TYPE timestampl, v_end_time TYPE timestampl, v_diff_w TYPE p DECIMALS 5.TYPES : BEGIN OF ty_vbrp, vbeln TYPE vbrp-vbeln, END OF ty_vbrp.DATA : lt_vbrp TYPE STANDARD TABLE OF ty_vbrp, ls_vbrp TYPE ty_vbrp.FIELD-SYMBOLS : <fs_vbrp> TYPE ty_vbrp.PARAMETERS p_count TYPE n LENGTH 6.* Start of selectionSTART-OF-SELECTION.* Get billing item data SELECT vbeln FROM vbrp INTO TABLE lt_vbrp UP TO p_count ROWS.END-OF-SELECTION.* 1 . Loop with work area GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp INTO ls_vbrp. ls_vbrp-vbeln = 1. MODIFY lt_vbrp FROM ls_vbrp. ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE :/(30) 'Loop with Work area', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.* 2 . Loop with work area inline declaration GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp INTO DATA(ls_vbrp_inline). ls_vbrp_inline-vbeln = 1. MODIFY lt_vbrp FROM ls_vbrp_inline. ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE:/(30) 'Loop with Inline Work area', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.* 3 . Loop with Field symbol GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp ASSIGNING <fs_vbrp>. <fs_vbrp>-vbeln = 1. ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE:/(30) 'Loop with Field Symbol', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.* 4 . Loop with Field symbol inline declaration GET TIME STAMP FIELD v_start_time. LOOP AT lt_vbrp ASSIGNING FIELD-SYMBOL(<fs_vbrp_inline>). <fs_vbrp_inline>-vbeln = 1. ENDLOOP. GET TIME STAMP FIELD v_end_time. v_diff_w = v_end_time - v_start_time. WRITE:/(30) 'Loop with Inline Field Symbol', v_diff_w. CLEAR : v_start_time, v_end_time, v_end_time.论断：
在两个测试后果中能够看出，loop到工作区实际上有一个内表到工作区的赋值过程。从工作区modify到内表也有一个赋值的过程。而在Field Symbol中则是间接批改了内表值。所以速度会比拟快很多。
所以在能用Field Symbol的中央尽量应用Field Symbol。