Error message generated by Oracle Rman backup

An error message is generated in alert. log during manual RMAN backup on Sunday.

Sat Jun 25 16:39:08 2012
Errors in file/home/Oracle/app/oracle/admin/XXX/udump/XXX_ora_22899.trc:
Sat Jun 25 16:39:08 2012
Errors in file/home/oracle/app/oracle/admin/XXX/udump/XXX_ora_22899.trc:
Sat Jun 25 16:39:08 2012
Errors in file/home/oracle/app/oracle/admin/XXX/udump/XXX_ora_22899.trc:

It's strange that RMAN does not report any error information. Please check the trc file:

* ** 16:18:53. 310
* ** Action name: (0000071 STARTED16) 16:18:53. 284
* ** Module name :( backup incr datafile) 16:18:53. 284
* ** Service name :( SYS $ USERS) 16:18:53. 284
* ** Session id: (192.52848) 16:18:53. 284

There is not much error information displayed, which is basically descriptive. Only metalink's forum has such a question and answer. One of ORACLE's support answers are rigorous:

There seems to be apparently no problem with the trace file that is getting generated.

However is it the full trace file or have you just pasted the heading of the trace file.

You are correct in interpreting that this is related to the backup.

If this is not the full tracefile you can update the thread with some more information or atleast the call stack part of the trace file.

If this is the full file, then there is nothing much that can be inferred from it, and can be ignored.

Okay, you can leave this issue alone.
Record it.
For a Data Manager, do not ignore any information generated by the database. Rigorous and necessary. -:)