ORA-00001: unique constraint (DEV.X_PK) violated

I have a java code that sends data to a web service, and a portlet that uses that data.

Data sent by java agent gets placed in TMP table, and merge procedure merges it into MAIN table used by portlet.

When running java agent I get the following error, although I ensure that no duplicate primary keys are sent:

ORA-00001: unique constraint (DEV.X_PK) violated
ORA-06512: at "DEV.PGK_Y", line 200
ORA-06512: at line 1

I tried turning off primary key constraint, but in vain. Then I tried to drop all tables used, and created them again开发者_StackOverflow社区. But still no luck...

Interestingly, I am able to manually insert data into TMP and run merge procedure, and there are no errors.

Any help is appreciated...

Enable SQL trace of the session and it should be pretty simple to find out what is causing the ORA-1.