Do you need to convert decimal value to hexadecimal representation? Then you should try this:

-- 
WITH DEMO AS (SELECT DECIMAL( 12345678.905 , 15, 3 ) AS DECVALUE -- 8 bytes internally 
              FROM SYSIBM.SYSDUMMYE ) 
--               
SELECT DECVALUE                                  AS DECVALUE_ORIGINAL, 
       PACK(CCSID 1208,DECVALUE)                 AS DECVALUE_PACKED, 
       LENGTH(PACK(CCSID 1208,DECVALUE))         AS LEN_DECVALUE_PACKED, 
       HEX( PACK(CCSID 1208,DECVALUE) )          AS X_DECVALUE_PACKED, 
       HEX(SUBSTR(PACK(CCSID 1208,DECVALUE) ,8)) AS X_DECVALUE_PACKED_STRIPPED 
FROM   DEMO 
;

Sample data displayed in a GUI (e.g. DbVisualizer):

The result is of type VARBINARY. You cannot mix  CHAR / VARCHAR and VARBINARY data but you can concatenate other converted strings. Example:

HEX(SUBSTR(PACK(CCSID 1208,DECVALUE) ,8,6 ) !! VARBINARY(X'050C',2))

In former versions of DB2 the attribute CHAR FOR BIT DATA has been used. The VARBINARY attribute is the appropriate replacement.