Performance Issue in modifying a ITAB

Hi SDNs.,

performance issue in modifying a internal table : code :

*-Modify LT_DOC with Object list number(OBKNR) from SER03

LOOP AT LT_SER03_HASH INTO LW_SER03.

IF ( LW_SER03-OBKNR IS NOT INITIAL ).

READ TABLE LT_DOC INTO LW_DOC WITH KEY MBLNR = LW_SER03-MBLNR

MJAHR = LW_SER03-MJAHR

ZEILE = LW_SER03-ZEILE BINARY SEARCH.

IF ( SY-SUBRC = 0 ). " AND ( LW_SER03-OBKNR IS NOT INITIAL ).

LW_DOC-OBKNR = LW_SER03-OBKNR.

LW_DOC-DATUM = LW_SER03-DATUM.

LW_DOC-UZEIT = LW_SER03-UZEIT.

MODIFY LT_DOC FROM LW_DOC INDEX SY-INDEX TRANSPORTING OBKNR DATUM UZEIT WHERE MBLNR = LW_SER03-MBLNR AND

MJAHR = LW_SER03-MJAHR AND

ZEILE = LW_SER03-ZEILE .

ENDIF.

ENDIF.

CLEAR: LW_DOC, LW_SER03.

ENDLOOP.

<b>could any one help me out in tuning this code...</b>

Thank you

RK S