WITH t AS
(
SELECT 1 seq, 500 amt FROM dual
UNION ALL SELECT 2, -1000 FROM dual
UNION ALL SELECT 3,  1000 FROM dual
UNION ALL SELECT 4,   500 FROM dual
UNION ALL SELECT 5, -4000 FROM dual
UNION ALL SELECT 6,  1000 FROM dual
)
-- Recursive SQL (11G)
, t1(seq, amt, v) AS
(
SELECT seq
     , amt
     , GREATEST(amt, 0) v
  FROM t
 WHERE seq = 1
 UNION ALL
SELECT a.seq
     , a.amt
     , GREATEST(b.v + a.amt, 0) v
  FROM t a
     , t1 b
 WHERE a.seq = b.seq + 1
)
SELECT * FROM t1
;

WITH t AS
(
SELECT 1 seq, 500 amt FROM dual
UNION ALL SELECT 2, -1000 FROM dual
UNION ALL SELECT 3,  1000 FROM dual
UNION ALL SELECT 4,   500 FROM dual
UNION ALL SELECT 5, -4000 FROM dual
UNION ALL SELECT 6,  1000 FROM dual
)
-- MODEL (10G)
SELECT *
  FROM t
 MODEL
 DIMENSION BY (seq)
 MEASURES (amt, 0 v)
 IGNORE NAV
 RULES
 AUTOMATIC ORDER
 ( v[ANY] = GREATEST(v[CV()-1] + amt[CV()], 0) )
;

http://www.gurubee.net/lecture/2203