How to associate the next value of a field in a table next to the field itself?

I have a calendar table where each date has a flag associated with it if it is a vacation. I would like to create a derived table in which each holiday date is associated with the immediately following work date. For the size of the calendar this query does the job but is onerous. Is there any way to simplify the code?

select a.data_oss hd, min(b.data_oss) next_wd
from mts_calendar a 
join mts_calendar b on b.mts != 'H' and b.data_oss > a.data_oss and b.data_oss < a.data_oss +10
where a.mts = 'H'
group by a.data_oss

The most efficient way to do that is not to use joins or subqueries at all, but window functions in a set of nested query blocks. There are actually a number of different ways this can be done. Here's one such way:

1. Start by querying all the data - not just the holidays.

2. Then use DECODE to NULL out the holidays in a derived column.

3. In a parent block, the FIRST_VALUE function with IGNORE NULLS and the proper windowing specification can easily get the next non-holiday date using that derived column from the inner block.

4. Once you've done that, it's simply a matter of filtering down to just holidays in the top-level block.

SELECT a.data_oss holiday_date,
       a.first_non_holiday_date
  FROM (SELECT a.*,
               FIRST_VALUE(non_holiday_date IGNORE NULLS) OVER (ORDER BY data_oss ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING) first_non_holiday_date
          FROM (SELECT a.*,
                       DECODE(mts,'H',NULL,data_oss) non_holiday_date
                  FROM mts_calendar a) a) a
 WHERE mts = 'H'
 ORDER BY 1