If you have the page space to support it, you can get by without TDSK space by 
using V-disk. It is always cleared very quickly, by CP, before it is used and 
does not pose the security problems that you find in T-disk. A large V-disk is 
also faster to format than is a T-disk of equal capacity.

Regards, 
Richard Schuh 

 

> -----Original Message-----
> From: The IBM z/VM Operating System 
> [mailto:ib...@listserv.uark.edu] On Behalf Of Alan Altmark
> Sent: Wednesday, September 16, 2009 6:51 PM
> To: IBMVM@LISTSERV.UARK.EDU
> Subject: Re: TDISK and SYSTEM CONFIG question.
> 
> On Wednesday, 09/16/2009 at 07:14 EDT, "Gentry, Stephen" 
> <stephen.gen...@lafayettelife.com> wrote:
> 
> > Further, and in the same manual,  it states that you can clear each
> T-DISK 
> > before it is reassigned.  It depends on your point of view but this
> seems 
> > contradictory. Clear, in my opinion, means the T-DISK 
> created with the
> DEFINE 
> > command is completely cleared. Of course clearing cylinder 0, in 
> > effect,
> makes 
> > the area unreadable.  Also one section of the manual seems 
> to say that
> the area 
> > is cleared at IPL time, the other section seems to say it is cleared
> before it 
> > is reassigned.
> 
> Clearing cyl 0 only does not prevent you from reading the 
> other cyls on the volume; it simply stops you from mounting 
> it in the "usual" fashion.
> 
> The z/VM Secure Configuration Guide tells you to enable 
> CLEAR_TDISK in SYSTEM CONFIG.  If you configure your system 
> much the way it is described in that book, your auditor won't 
> have any arguments with you.
> 
> Alan Altmark
> z/VM Development
> IBM Endicott
> 

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