Rather than IOS, the channel should do the checking.  For DASD, the SetFileMask 
command is used to prevent seeking outside of the dataset's extents.  Don't 
remember if there's anything similar to prevent rewinding over tape marks.  


 > Date: Wed, 3 Oct 2012 09:15:50 -0500
> From: john.mck...@healthmarkets.com
> Subject: Re: How to get a tape's DSCB
> To: IBM-MAIN@LISTSERV.UA.EDU
> 
> It would be very difficult and have a lot of overhead to have IOS (not iOS) 
> check every CCW chain for "suspect" CCWs. It is given as one of the reasons 
> why RACF does not implement PDS member security. It's too easy to update a 
> PDS member via TTR without any member name anywhere in sight.
> 
> -- 
> John McKown
> Systems Engineer IV
> IT
> 
> Administrative Services Group
> 
> HealthMarkets®
> 
> 9151 Boulevard 26 • N. Richland Hills • TX 76010
> (817) 255-3225 phone •
> john.mck...@healthmarkets.com • www.HealthMarkets.com
> 
> Confidentiality Notice: This e-mail message may contain confidential or 
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> contact the sender by reply e-mail and destroy all copies of the original 
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> 
> 
> > -----Original Message-----
> > From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU]
> > On Behalf Of Paul Gilmartin
> > Sent: Wednesday, October 03, 2012 9:09 AM
> > To: IBM-MAIN@LISTSERV.UA.EDU
> > Subject: Re: How to get a tape's DSCB
> > 
> > On Wed, 3 Oct 2012 07:55:44 -0500, McKown, John wrote:
> > 
> > >And, just to be complete, you are assuming that your customers will be
> > using IBM standard tape labels. Granted, who doesn't? But it is an
> > assumption. Also, remember that in many shops, use of BLP to read the
> > tape labels can be protected via the tape management system, or even
> > with RACF now-a-days. Does not apply if you use EXCP to REW the tape,
> > of course.
> > >
> > Inconsistency.  Either the REW CCW or EXCP itself should be likewise
> > RACF protected or protected by the tape management system.  The
> > unprivileged user should have no opportunity to overwrite labels of
> > library tapes.
> > 
> > I suppose a virtual tape might have a virtual label, and any attempt
> > to invalidate the label should fail or be ineffective.
> > 
> > -- gil
> > 
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