Cloning database: AIX + TSM

Oracle 10.2.0.3 (RAC)
AIX 5.3.?
TSM  v??.??

Have an Oracle RAC environment on AIX.
Attempting to clone the environment to a different AIX machine.

Used TSM to copy raw devices from source to tape using commands like:
dsmc backup image /dev/dcert_00000001

Used TSM to restore to raw devices from tape to target using commands 
like:
dsmc restore image /dev/dcert_00000001

When we tried to start the new instance/database, we got errors saying 
that the
control file was not readable.  Copied the control file(s) again, using 
"DD" commands.
After moving the new copies of the control files, the database came up 
fine.

Since the data files and control files were copied using the same 
technique, we really expected the 
instance to fail with similar message about the data files being 
corrupted.

Any clue as to why Oracle would tolerate the data files when it refused 
the contol files?

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