System datafile corruption.

Guys,

        I have a system datafile that returns dbv errors for a SYSTEM datafile.

The fault has existed for a long time undiscovered so recovery from backup is not possible. The database still does not exhibit any problems except for dbv!
The errors are all 'Block Type = Undo data block', so I assume the fault is in the system rollback segment.

I'm sure I can't drop/recreate the SYSTEM rbs, so does anyone have any suggestions apart from a full export and import?

Dbv extract is below:
>

Block Checking: DBA = 67108870, Block Type = Undo data block

ERROR: Undo Block Corrupted. Error Code = 2008

ktu4ubck: size(108) of undo record #1 corrupted.

UNDO BLK HEADER: xid: 0x0000.08a.00000151 seq: 0x198 cnt: 0x4d irb: 0x4d icl: 0x0 flg: 0x000
0  

 Rec Offset | Rec Offset | Rec Offset | Rec Offset | Rec Offset

0x00 0x1fe8 | 0x01 0x1f80 | 0x02 0x1f2e | 0x03 0x1ee0 | 0x04 0x1e76

.
.
0x4b 0x027c | 0x4c 0x0212 | 0x4d 0x01b0

Hex dump:

0x000b6b94(+0000): 00 0a 00 10 00 3c 00 10 00 02 00 00 2a 11 00 00

.
.
0x000b6bf4(+0060): 00 9d 00 00 78 bc 01 00

>

grep 'Block Type' dbv_log | wc -l

     127

Regards,
Mike Jenner
Database Administrator

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