Hi

From metalink:
Error: ORA 2049
Text: timeout: distributed transaction waiting for lock
-------------------------------------------------------------------------------
Cause: Exceeded ISTRIBUTED_LOCK_TIMEOUT> seconds waiting for lock.
Action: treat as a deadlock


*** Important: The notes below are for experienced users - See [NOTE:22080.1]

Explanation:
Ignore the "Action" above - this is non-sense.

Basically ORA 2049 is signalled if:

a) you are waiting on another sessions TX enqueue
(Eg: usually you are waiting for a row lock)

AND b) you are performing a distributed operation.
Eg: You are using a DB link for something, even if it is only a
select

AND c) You wait for longer than 'distributed_lock_timeout'

The use of a DB Link opens you up to distributed rules of operation
even if you only READ from it.

You can either increase the timeout OR handle the ORA 2049 as a 'try again'
exception that is not fatal. This mechanism exists to prevent deadlock
so any handling of 'TRY AGAIN' should include an escape clause to prevent
deadlock.

Example:
Session 1
~~~~~~~~~
Session 2
~~~~~~~~~
update t2@LINK set b=4 where b=3;


select * from dual@LINK;
update t2 set b=4 where b=3;
^^ ORA 2049
OR EVEN
update t2 set b=4 where b=3;


select * from dual@LINK;
update t2 set b=4 where b=3;
^^ ORA 2049