SQL & PL/SQL :: How To Implement Pagination For Large Table Joins

I have two large tables(rptbody and rpthead) which has over millions or even more records. Below is the table schema

describe rpthead
Name Null Type
--------------------------- -------- -------------
RPTNO NOT NULL NUMBER
RPTDATE NOT NULL DATE
RPTD_BY NOT NULL VARCHAR2(25)
PRODUCT_ID NOT NULL NUMBER
[code]...

What I want is getting all data if the referenced RPTNO belongs to a particular product_id from rptbody table, here's the sql

SELECT t0.LINENO, t0.COMMENTS, t0.RPTNO, t0.UPD_DATE
FROM RPTBODY t0
WHERE
(
t0.RPTNO IN
(
SELECT t1.RPTNO FROM RPTHEAD t1 where t1.PRODUCT_ID IN ('4647')
)
)
ORDER BY t0.LINENO

Since the result set is pretty large, so my application(think it as c couple of jobs, each job should be finished in a time window) can only process a subset of all data, so I need pagination so that the next job can continue the processing until all data is processed, below is the SQL with pagination

select * from (
select a.*, ROWNUM rnum from
(
SELECT t0.LINENO, t0.COMMENTS, t0.RPTNO, t0.UPD_DATE
FROM RPTBODY t0
WHERE
(
[code]....

As you can see each query will take 100 rows from the db. The problem for now is that the query taking too much of time(10+ mins), I know the slowness is due to "ORDER BY t0.LINENO", but it's required for pagination.