[Info-vax] Greater than approx 16GB disk leads to UNXSIGNAL crash

[Volker Halle]

Antonio,

this was a 'known problem' at it's time - mostly V6.2.

There even was/is a CANASTA rule describing this problem and a workaround...

CANASTA was the automatic Crashdump Analysis Tool, which I maintained for about a decade while at Digital/Compaq/HP. I still claim to be the person, which has seen more OpenVMS crash footprints than anyone else ;-)

The problem itself seems to be in MOUNT, when setting up the geometry of the disk. Solutions i.e. patches may exist in the V7.2 remedial stream or higher.

WORKAROUND:

Configure a smaller disk on the controller.  After configuring the smaller
disk, mount the disk and do a $ SHOW DEVICE/FULL.  Perform the following
calculation using the numbers from the $ SHOW DEVICE/FULL output.

sectors per track * tracks per cylinder * total cylinders = total blocks.

If the calculation works, the disk is OK to use.

With ANALYZE/SYSTEM:

SDA> READ SYS$SYSTEM:SYSDEF
SDA> SHOW DEV DKcnnn
...
SDA> exa ucb+ucb$l_maxblock
UCB+000C4:  021EB1B0   "°±.."
SDA> eva (@(ucb+ucb$b_sectors)&FF)*(@(ucb+ucb$b_tracks)&FF)*(@(ucb+ucb$w_cylinders)&FFFF)
Hex = 0020B32C   Decimal = 2143020

This crash has also been seen on a CHARON-VAX (Stromasys commercial VAX emulator) and could be  prevented  by using the geometry statement to set a 'valid' geometry, e.g.

SET DKA geometry[200] = "125/16/17783"	! s=sectors t=tracks c=cylinders   (disk size about 18 GB)

Don't know if simh supports setting the disk geometry.

Volker.