transactions and Oracle dblink

I have 2 dbs, let's call them writedb and readdb. Readdb has a dblink to writedb and a view to a table over that dblink.

I do an update on writedb to that table which view points to and then read from that table over the dblink. I appear to be seeing old values for seconds after the transaction commits even if I set isolation level to SERIALIZABLE.

Does this make any sense?

On writedb:

create table mk.dblink_test (
id varchar2(16),
status varchar2(16));

insert into mk.dblink_test
SELECT rownum, 'ACTIVE'
FROM   dual
CONNECT BY LEVEL <= 1000000;

On readdb:

CREATE DATABASE LINK DBL_TEST CONNECT TO mk IDENTIFIED BY password USING 'writedb:1521/qa'

The SQL that updates writedb directly:

update mk.dblink_test
set status = 'DONE'
where id = '1';
commit;

Now the situation with SQL which get dirty reads is weird. The following simpler query

SELECT r.status
FROM mk.dblink_test@DBL_TEST r
WHERE r.id = '1';
commit;

does not appear to exhibit the problem. But a more complex version:

SELECT r.status
FROM mk.dblink_test@DBL_TEST r
LEFT OUTER JOIN (SELECT '3' status from dual) optout ON optout.status = r.status
WHERE r.id = '1';
commit;

reproduces it 90% reliably. The steps to reproduce:

1. launch sqlplus and connect to the readdb


2. run the read query, get status 'ACTIVE'


3. run the update query against the writedb in a different sqlplus


4. go back to the sqlplus from step (1), launch the read query from step (2) and get 'ACTIVE' again


5. repeat read query same as in step 4 -- get the correct 'DONE' response.