2262573 - Error in Phase EU_CLONE_MIG_DT_RUN or EU_CLONE_MIG_UT_RUN cannot CREATE UNIQUE INDEX; duplicate key found

• During an upgrade using the Software Update Manager (SUM) with the Database Migration Option (DMO), an error occurs in phase EU_CLONE_MIG_DT_RUN or EU_CLONE_MIG_UT_RUN
• The error message is similar to
  

  DbSl Trace:   execute(), rc=1, rcSQL=349
  DbSl Trace: EXECUTE on connection 0, rc=349
  ERROR exec_ddl_stmt: (DB) ERROR: DDL statement failed
   (ALTER TABLE "<tablename>" ADD CONSTRAINT "<tablename>~0" PRIMARY KEY ( "<field1>", "<field2>", "<field3>" ) )
   DbSlExecute: rc = 99
    (SQL error 349)
    error message returned by DbSl:
  cannot CREATE UNIQUE INDEX; duplicate key found:  [5] Several documents with the same ID exist in the index;<schema>:<tablename>.$trexexternalkey$ content not unique, cannot define unique constraint. rowCount != distinctCount
  (IMP) INFO: starting create for object "<tablename>" of type "unload" #20151121093656

  Or
  

  (HDB) ERROR: exec_ddl_stmt: DDL statement failed (ALTER TABLE "<tablename>" ADD CONSTRAINT "<tablename>~0" PRIMARY KEY ( "<field1>", "<field2>", … ) ) 
  (HDB) ERROR: DbSlExecute: rc = 99
  (HDB) ERROR: dbcode = 349
  (DB) ERROR: cannot CREATE UNIQUE INDEX; duplicate key found
  (HDB) ERROR: DDL statement failed (ALTER TABLE "<tablename>" ADD CONSTRAINT "<tablename>~0" PRIMARY KEY ( "<field1>", "<field2>", … ) )
  (HDB) ERROR: DbSlExecute: rc = 99

DMO using Software Update Manager (SUM) tool

(IMP) ERROR: dbcode = 349 ,no DDL for, DDXTF, build_ddl_stmt, exadata, EU_CLONE_MIG_UT_RUN, duplicate key found, reposrc, performance, EU_CLONE_MIG_DT_RUN, EU_CLONE_MIG_DT_IMP, EU_CLONE_MIG_UT_IMP , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , Problem