[Info-vax] Alerting on tape insert

[Rich Jordan]

On Oct 9, 6:54 pm, Stephen Hoffman <seaoh... at hoffmanlabs.invalid>
wrote:
> On 2012-10-09 23:35:03 +0000, Rich Jordan said:
>
> > Does a SCSI attached tape drive send any kind of notification to VMS
> > (ignored by default or not) when a tape is loaded into the drive, if
> > the drive is currently unallocated and not being waited on by any
> > program?
>
> The SCSI device doesn't know from its allocation status, etc.
>
> > I'm just wondering if there's a way to trip an event to have
> > a program check that media for various characteristics (write enabled,
> > label, etc)
>
> Polling.  Or hold an I/O channel to the device, and ask the drive.
>
> > I can poll (using a program that issues a QIO with IO$_PACKACK) to see
> > if the media is present/loaded (and then doing whatever else is needed
> > to verify its writable status) but I'm wondering if there's a way for
> > VMS to let me know a tape has been loaded in a specific drive without
> > polling.
>
> VMS doesn't include a notification mechanism.
>
> > I suppose I could leave a program that issues a mount to the drive and
> > just 'waits' for a tape to show up but that seems inelegant.
>
> If you're writing an app, there are SCSI-level notifications available
> from various drives.  VMS doesn't use them, but the command packet
> interface does allow an application to request them from a SCSI device.
>  But that means the drive is going to have an application I/O channel,
> and some other baggage.
>
> And if you're tossing SCSI-level commands at the SCSI device, it
> doesn't need to be mounted.
>
> Dig up the T10 SCSI specs and start reading.  I don't remember off-hand
> if the notification sequence is in the base SCSI commands
> documentation, or in the block device commands.  But I think it's in
> the latter.
>
> --
> Pure Personal Opinion | HoffmanLabs LLC

Thanks Hoff.  I expect that would be interesting but I doubt I'll have
time, so probably going to be polling at a higher level.  But I'll dig
up the docs to see.

Rich