[Simh] VAX Tape Emulation?

[Larry Baker]

The answer is: the rmt protocol is not sufficient to support Backup.  From the Multinet Installation and Administrator's Guide (http://www.process.com/docs/multinet5_5/install_admin.pdf):

About the RMT Client

The RMT client MULTINET RMTALLOC is used for accessing tape or CD-ROM drives on remote hosts over TCP (using RSHELL). If restrictions apply where RSHELL does not work, or if RSHELL outputs spurious login messages or greetings, RMTALLOC does not work. RMTALLOC depends on an RMT server to function properly. RMTALLOC creates a pseudo device that appears as an OpenVMS physical device to the OpenVMS BACKUP, COPY, and other utilities. The pseudo device is named RMTx:, x is the unit number. The actual tape or CD-ROM drive can be on another MultiNet OpenVMS system or on any host running the RMT server, such as those running the BSD or SunOS UNIX operating system.

For CD-ROM, RMTALLOC treats the drive as a file system, which speeds file access.

There are some limits to the types of tape devices you can access on other operating systems and the amount of control available. Because UNIX tapes and tape drivers cannot write variable-length blocks and do not allow skipping forward over records between read operations, they cannot be used with OpenVMS BACKUP or COPY commands. 

Larry Baker
US Geological Survey
650-329-5608
baker at usgs.gov



> On 25 Jan 2018, at 12:57:46 PM, Clem Cole <clemc at ccc.com> wrote:
> 
> The question is do the standard tape utilities know how to exploit it -- i.e. the moral equiv of the UNIX sequence:  cmd -f - | rmt host    
> 
> I thought CJ and Co had some way to make that work in mid 90's versions of VMS but I've forgotten the details (many beers ago).
> 
> 
> ᐧ
> 
> On Thu, Jan 25, 2018 at 3:11 PM, Tony Nicholson <tony.nicholson at computer.org> wrote:
> On Fri, 26 Jan 2018 at 07:00, Larry Baker <baker at usgs.gov> wrote:
> Clem,
> 
> MultiNet included rmt support.  I do not know which versions included it or whether MultiNet has a Hobbyist License.
> 
> 
> Process Software’s Multinet  and PMDF for OpenVMS have had hobbyist licenses for a long time now. All you need to do is apply and provide an LMF checksum value from your hobbyist licence - see the link from the OpenVMS Resources page at
> 
> http://www.process.com/psc/resources/openvms-resource-center/
> 
> Tony
> -- 
> Tony Nicholson <tony.nicholson at computer.org>
> 

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