set transaction use rollback segment SYSTEM;
delete from sys.pending_trans$ where local_tran_id = ;
delete from sys.pending_sessions$ where local_tran_id = ;
delete from sys.pending_sub_sessions$ where local_tran_id = ;
commit;

Example:
--------
The following query reports a dist. txn. in prepared state
select local_tran_id, state from dba_2pc_pending;
LOCAL_TRAN_ID STATE
---------------------- ----------------
1.92.66874 prepared

Given that a transaction id is composed of triple,
'1.92.66874' is located in rollback segment# 1. To find out the list of
active transactions in that rollback segment, use:

SELECT KTUXEUSN, KTUXESLT, KTUXESQN, /* Transaction ID */
KTUXESTA Status,
KTUXECFL Flags
FROM x$ktuxe
WHERE ktuxesta!='INACTIVE'
AND ktuxeusn= 1; <== this is the rollback segment#

no rows selected

rollback force '1.92.66874';

ORA-02058: no prepared transaction found with ID 1.92.66874

set transaction use rollback segment SYSTEM;

delete from sys.pending_trans$
where local_tran_id = '1.92.66874';

delete from sys.pending_sessions$ where local_tran_id = '1.92.66874';

delete from sys.pending_sub_sessions$ where local_tran_id = '1.92.66874';

commit;

execute DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('transanction_id');

ORA-1591: lock held by in-doubt distributed transaction 1.92.66874

select local_tran_id, state from dba_2pc_pending
where local_tran_id='1.92.66874';

no rows selected

SELECT KTUXEUSN, KTUXESLT, KTUXESQN, /* Transaction ID */
KTUXESTA Status,
KTUXECFL Flags
FROM x$ktuxe
WHERE ktuxesta!='INACTIVE'
AND ktuxeusn= 1; /* <== Replace this value with your txn undo seg#
Which is displayed in the first part of
the transaction ID */

KTUXEUSN KTUXESLT KTUXESQN STATUS FLAGS
---------- ---------- ---------- ---------------- ------------------------
1 92 66874 PREPARED SCO|COL|REV|DEAD

commit force '1.92.66874';

ORA-02058: no prepared transaction found with ID 1.92.66874

alter system disable distributed recovery;

insert into pending_trans$ (
LOCAL_TRAN_ID,
GLOBAL_TRAN_FMT,
GLOBAL_ORACLE_ID,
STATE,
STATUS,
SESSION_VECTOR,
RECO_VECTOR,
TYPE#,
FAIL_TIME,
RECO_TIME)
values( '1.92.66874', /* <== Replace this with your local tran id */
306206, /* */
'XXXXXXX.12345.1.2.3', /* These values can be used without any */
'prepared','P', /* modification. Most of the values are */
hextoraw( '00000001' ), /* constant. */
hextoraw( '00000000' ), /* */
0, sysdate, sysdate );

insert into pending_sessions$
values( '1.92.66874',/* <==Replace only this with your local tran id */
1, hextoraw('05004F003A1500000104'),
'C', 0, 30258592, '',
146
);

commit;

commit force '1.92.66874';

delete from pending_trans$ where local_tran_id='1.92.66874';
delete from pending_sessions$ where local_tran_id='1.92.66874';
commit;
alter system enable distributed recovery;

alter system enable distributed recovery;
connect / as sysdba
COMMIT;
Use following query to retrieve the value for such _smu_debug_mod parameter:

col Parameter for a20
col "Session Value" for a20
col "Instance Value" for a20

SELECT a.ksppinm "Parameter",b.ksppstvl "Session Value",c.ksppstvl "Instance Value"
FROM x$ksppi a, x$ksppcv b, x$ksppsv c
WHERE a.indx = b.indx AND a.indx = c.indx AND a.ksppinm = '_smu_debug_mode'
/

-- set it temporarily to 4:

alter system set "_smu_debug_mode" = 4; /* if automatic undo management
is being used */
-- in 9.2x alter session can be used instead.

commit; /* this is to prevent the ORA-01453 in purge_lost_db_entry call */

exec dbms_transaction.purge_lost_db_entry( '1.92.66874' );

SQL> commit;

SQL> alter system set "_smu_debug_mode" = ;

SQL> commit;

SQL> SELECT LOCAL_TRAN_ID,STATE FROM DBA_2PC_PENDING;

LOCAL_TRAN_ID STATE
----------------- -----------
44.88.85589 prepared

SQL> SELECT KTUXEUSN, KTUXESLT, KTUXESQN, /* Transaction ID */
KTUXESTA Status,
KTUXECFL Flags
FROM x$ktuxe
WHERE ktuxesta!='INACTIVE'
AND ktuxeusn= 44; /* <== Replace this value with your txn undo seg#
Which is displayed in the first part of
the transaction ID */

KTUXEUSN KTUXESLT KTUXESQN STATUS FLAGS
---------- ---------- ---------- ---------------- ------------------------
44 88 85589 PREPARED SCO|COL|REV|DEAD

SQL> Commit force 44.88.85589;
SQL> rollback force 44.88.85589;

EXECUTE DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('44.88.85589');
BEGIN DBMS_TRANSACTION.PURGE_LOST_DB_ENTRY('44.88.85589'); END;

*
ERROR at line 1:
ORA-06510: PL/SQL: unhandled user-defined exception
ORA-06512: at "SYS.DBMS_TRANSACTION", line 94
ORA-06512: at line 1

delete from sys.pending_trans$ where local_tran_id = '44.88.85589';
delete from sys.pending_sessions$ where local_tran_id = '44.88.85589';
delete from sys.pending_sub_sessions$ where local_tran_id ='44.88.85589';
commit;