There are a few details missing.
Are you writing to the same VTL system?
If so you may be seeing TSM rebuild the aggregates which effectively changes 
the data the VTL sees.
If it is a new VTL then the first data is always new and has nothing to 
de-duplicate against.

Andy Huebner

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
zinv1
Sent: Thursday, May 23, 2013 12:03 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Increase in unique data

Currently i am in the process of exporting by tape to a new tsm server version 
6.3. Our old TSM server was run with a VTL with Deduplication. During the 
process of the migration i see a big increase in unique data being stored on 
the Dedup engine. I just wanted to know if during the export operations if the 
data is altered in some way which result in the dedupe engine seeing data that 
is already stored as new data?

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