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...

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