ORA-02055: Distributed update operation failed; rollback required

Every DBA at least one time faced ORA-02055 exception. It may be occur on several reasons. Here is symptom and reason.

ORA-02055:	distributed update operation failed; rollback required
Cause:	a failure during distributed update operation may not have rolled back all effects of the operation. Since some sites may be inconsistent, the transaction must roll back to a savepoint or entirely
Action:	rollback to a savepoint or rollback transaction and resubmit

It will be helpful checking DBA_2PC_PENDING data dictionary view 

select * from DBA_2PC_PENDING order by fail_time

--take local_tran_id or global_tran_id

example 8.44.2012311

Then enable distributed recovery and execute below statements using:

      

ALTER SYSTEM ENABLE DISTRIBUTED RECOVERY

      

execute dbms_transaction.rollback_force('8.44.2012311');

      

execute dbms_transaction.purge_lost_db_entry('8.44.2012311')

Source:

http://ora-02055.ora-code.com/

http://docs.oracle.com/cd/B19306_01/server.102/b14231/ds_txnman.htm

http://www.dbmotive.com/ora-02055-distributed-update-operation-failed-rollback-required/