JDBC Sender - ORA-08177 on UPDATE, but Table is updated - no message

Question

Hi,
I have a problem with JDBC Adapter:
I use a JDBC Sender adapter, polling every minute on an Oracle DB.
I use isolation level "serializable".
No what happens sometimes is, that the update statement fails because of "ORA-08177: can't serialize access for this transaction", so no message is forwarded to the IS. Curiously, the entries in the table are updated, so the JDBC Driver seems to update the data anyways.
Has anybody experience with similar problems? This is a really hard issue because no messages are transmitted althought the condition field in the table is updated and everything seems normal. Also the status light of the communication channel will be green again after a while, so it is really hard to trace.
System:
XI 3.0 SP20
ORACLE 8.1.7.4
I use the following statements with a rownum limit:
select ... from TABLE where CONDITION = '_to_send' AND rownum <= 20 order by NACHRICHT_ID
update TABLE set CONDITION = '_sending' where PRIMARY_KEY in (select PRIMARY_KEY from TABLE where CONDITION = '_to_send' and rownum <= 20)
(just to complete the picture...)
This message goes to BPM, where it is split into single messages. These messages are processed separately, and after an successfull processing an update statement is sent back to the DB:
update TABLE set CONDITION = '_processed' where PRIMARY_KEY = <PK of processed message>
So the condition "_sending" is an interim status for the messages sent to BPM, but not finally processed.
What happens is, that the receiver of the messages complained about missing messages. I could find some messages in the interim status, but no message has ever been sent.
I appreciate any help.
Thank you very much.

Answer 1

Sainath Chutke wrote:
As you have used the Isolation level as serialiable whenever the transaction fails the data gets updated because once the transaction reaches the end of the adapter level processing " the update statemnets gets executed " Irrespective of whether the transaction is sucessful or failure."
Curiously, the select statement does not throw the error, the update statement does. But even though the update statement does not work (ORA-08177), it works (rows in DB are updated). That is what causes headache to me.
Try to change the Isolation level and get the message id generated using an UDF.´
Sorry, but I do not completely understand what you suggest here.
My needs are:
- select rows that fulfill condition (limit to a max number per poll interval)
- update the selected rows to not fulfill the condition any more (to not double sent data)
- the update statement must update exactly the same rows that have been selected before (transaction)
or in other words:
I need to make sure the data is sent only once and exactly once.
If your idea can satisfy these needs, I kindly ask you to explain it more detailed.
Thank you very much.