while downloading file to application server its overwriting the earlier fi

hi if i am using below code with date time stamp the file is downloaded to the application server correctly and each time i execut eht program a difference file is generated as date time stamp differs each time but

whne i remove the date time stamp ie sy-datum and sy-uzeit as we dont need to display the date time stamp with the file each time i execute the program a file is generated but it overwrites the ealier existing file please suggest as each time it shoul generate a new file....

Concatenate file name sy-datum sy-uzeit '.txt' into v_datetimefile

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• file on Appplication Server is selected

CALL FUNCTION 'FILE_GET_NAME'

EXPORTING

• CLIENT = SY-MANDT

logical_filename = 'ZFILE'