SCSI Pass-Through Programmer's Guide

Device Configuration using SYSGEN
WARNING: Sending SPT commands to a device in use by MPE or other applications may
result in data loss, data corruption and/or System Aborts. We do not recommend sending
SPT commands to Disks with MPE/iX Volumes present nor should one access tapes devices
which are used for normal back-up or data logging purposes. Rule of thumb: Don’t do SPT
to tape or disk media you cannot recover at a time you don’t wish to cause a system outage.
When a device is added using SYSGEN/IOCONFIG, based on the device ID supplied, a
physical manager (pmgr, a.k.a Device Manager or DM) is assigned to the device. The DM
used by a particular device can be seen when a ‘lp’ (list path) of the device’s physical path is
done. The following DMs (pmgrs) in MPE/iX support SPT calls:
scsi_disc_dm (discs),
scsi_disk_and_and_array_dm (disc arrays),
scsi_tape_dm (DDS tape drives),
scsi_tape2_dm (DLT tape drives),
mo_scsi_pthru_dm (MO devices).
It is recommended that most users of SPT consider configuring SCSI devices with device
ID=PTHRU which results in using the mo_scsi_pthru_dm pmgr. This device driver
provides basic connectivity to SCSI devices without a lot of overhead.
We can also use certain generic IDs to configure devices. For instance, a disc can be
configured with ID=LVDDISK, disc arrays with ID=HPDARRAY and a tape with ID=DDS.
The appropriate pmgr is set based on the ID. This will still allow MPE/iX to use these
devices. But, please be cautioned that SPT access to such devices may corrupt the MPE/iX
functionality, meaning that MPE/iX may not be able to read/write to the device.
One may also use more common HP product IDs (e.g HPC1537A – a DDS tape drive) for
HP devices As SCSI commands can also be issued to these devices via the SPT interface
outlined in the previous section. Again, these devices will look just like other MPE/iX
Devices and may therefore cause one to accidentally corrupt data.
For SPT access to devices that are not supported by MPE/iX, it is recommended to use
device ID=PTHRU which results in using the mo_scsi_pthru_dm pmgr.
The following is a sample configuration of different device types:
LDEV: 1 DEVNAME: 00000001 OUTDEV: 0 MODE:
ID: HPDARRAY RSIZE: 128 DEVTYPE: DISC
PATH: 0/0/1/1.15.0 MPETYPE: 4 MPESUBTYPE: 2
CLASS: DISC SPOOL
LDEV: 7 DEVNAME: 00000007 OUTDEV: 0 MODE:
ID: DDS RSIZE: 128 DEVTYPE: TAPE
PATH: 0/0/2/0.6.0 MPETYPE: 24 MPESUBTYPE: 7
CLASS: TAPE TAPE2 DDUMP TAPE1
- 11 -