Find MERGE JOIN CARTESIAN

Hi All, I've a query that is producing a CARTESIAN product. This query never completes in production, but due to small data it completes in DEV.  Is there a way where I can find from the query where the problem is and the solution for that ?

The query is

explain plan for

SELECT CD.DECISIONFROMDATE , CD.DECISIONTODATE , CDG.CONCERNROLEID , PD.CASEID , CH.INTEGRATEDCASEID , CRAI.ALTERNATEID , P.DATEOFBIRTH , AN.SURNAME , AN.FIRSTFORENAME , CR.PREFERREDLANGUAGE , PD.PRODUCTTYPE , AIHN.ALTERNATEID , AIHN.CONCERNROLEALTERNATEID , CH.STATUSCODE ,

CD.RESULTCODE                              

FROM curam_s1_user.MCSSCASEDECISIONGROUP CDG

INNER JOIN curam_s1_user.CASEDECISION CD ON CDG.CASEDECISIONID= CD.CASEDECISIONID