Field symbols are not asssigned

Hi all,

I have to us field symbols instead of work area, i am getting an error as field symbols are not assigned,

This is how i declared filed symbols.

DATA:TS_BKPF TYPE TABLE OF y_bkpf ,

FIELD-SYMBOLS: <fs_y_bkpf> TYPE ANY TABLE.

.FIELD-SYMBOLS: <fs> TYPE y_bkpf.

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LOOP AT ts_bkpf ASSIGNING <fs>.

e_struct1-bukrs = <fs>-bukrs.

when i debug, fs has no value assigned to it.

Please Help.