Normally, when you want to read the file from application server, you will have 5 steps:

1. Open file in application server by statement:
   

   OPEN DATASET file_name FOR INPUT IN TEXT MODE.

2. Checking the file is opened sucessfully by SY-SUBRC = 0
3. After checking, you can read data from file by statement:
   

   READ DATASET file_name INTO itab.  
   Note: This statement should be in DO statement

4. Append data to internal table
5. Close file by statement:
   

   CLOSE DATASET file_name

Example

DATA: BEGIN OF i_tab OCCURS 0,
        text(100),
      END OF i_tab,
      gv_dataset1(30) VALUE ’/temp/testfile.txt’.

OPEN DATASET gv_dataset1 FOR INPUT IN TEXT MODE. 
  DO. 
    IF SY-SUBRC <> 0. 
      EXIT. 
    ENDIF. 
    READ DATASET gv_dataset1 INTO i_tab. 
    APPEND i_tab. 
    CLEAR i_tab. 
  ENDDO. 
CLOSE DATASET gv_dataset1.