第一步：初始化server group ,server group 可以用RZ12进行维护，参数支直复制即可，不要修改。
CONSTANTS: serv_group LIKE rzllitab-classname VALUE 'JOBRUN'.
CALL FUNCTION 'SPBT_INITIALIZE'
EXPORTING
group_name = serv_group
* IMPORTING
* MAX_PBT_WPS =
* FREE_PBT_WPS =
EXCEPTIONS
invalid_group_name = 1
internal_error = 2
pbt_env_already_initialized = 3
currently_no_resources_avail = 4
no_pbt_resources_found = 5
cant_init_different_pbt_groups = 6
OTHERS = 7
.
第二步：分别写多个FM的调用，注意：如果多个FM都共用的参数，数据写在主程序中，然后用参数传到FM里。
CALL FUNCTION 'Z_BAPI_FM1'
STARTING NEW TASK 'FM1TASK' DESTINATION IN GROUP serv_group
PERFORMING sub_fm1_back ON END OF TASK
TABLES
date_ra = date_ra.
CALL FUNCTION 'Z_BAPI_FM2'
STARTING NEW TASK 'FM2TASK' DESTINATION IN GROUP serv_group
PERFORMING sub_FM2_back ON END OF TASK
TABLES
date_ra = date_ra.
第三步.FM执行完之后数据反回，数据返回的参数是全局的，在Z_BAPI_FM*中对全局参数进行赋值。
FORM sub_fm1_back USING name.
RECEIVE RESULTS FROM FUNCTION 'Z_BAPI_FM1'
TABLES
ret_par = gdt_ret_pars "返回的参数
return = gdt_gr_return.
APPEND LINES OF gdt_gr_return TO gdt_return.
gr_flag = 'X'. "这个很重要，根据这个参数判断FM是否执行完毕
ENDFORM. "sub_fm1_back
FORM sub_fm2_back USING name.
RECEIVE RESULTS FROM FUNCTION 'Z_BAPI_FM2'
TABLES
returnpo = gdt_ret_pos
return = gdt_returnpo_return.
APPEND LINES OF gdt_returnpo_return TO gdt_return.
returnpo_flag = 'X'.
ENDFORM. "sub_fm2_back
第四步：收尾工作，判断各个FM是否执行完毕
WAIT UNTIL gr_flag = 'X' AND returnpo_flag = 'X' .
ret_pars[] = gdt_ret_pars. “返回的结果
returnpo[] = gdt_ret_pos. “返回的结果
APPEND LINES OF gdt_return TO return. “最终返回的return ，一般FM都有返回值，返回错误，警告等信息。
