The values shown in the "Read Formats" and "Write Formats" fields of Query 
DRive output are the values that can be specified with the FORMAT parameter of 
the device class definition: they report capabilities, not what is in force at 
the moment.  Your Devclass definition governs actual I/O methodology - where I 
would not use a specification of "DRIVE" unless there was a really good reason 
to not explicitly specify exactly what you want to happen, such as 3592C.  
Taking defaults can be perilous.

    Richard Sims

On Jul 7, 2010, at 7:36 AM, Mehdi Salehi wrote:

> Hi,
> The format of a device class is set to "drive" and "query drive" shows the
> read and write format is "3592C,3592". The question is when does TSM uses
> the compressed format? In a TSM 5.3 system, almost all volumes are 300GB (q
> vol) except one of them. I cannot explain why TSM have not treated this one
> like other volumes while cartridges are of the same type.
> 
> Thanks