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) option, errors may occur in the following phases.

1. DMO without system move:

   - EU_CLONE_MIG_DT_RUN

   - EU_CLONE_MIG_UT_RUN

2. DMO with system move:

   - EU_CLONE_MIG_*_IMP

The error message encountered in these phases is similar to the following messages found in the SUM logs.

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 option using 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, EU_CLONE_MIG_ , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , Problem