You can write the system dump file to a device other than
the system disk (DOSD) on OpenVMS systems. This is especially useful
in large-memory systems and in clusters with common system disks
where sufficient disk space is not always available on one disk
to support customer dump file requirements.
Requirements for DOSD are somewhat different on Alpha and
I64 systems than on VAX systems. On all systems, however, you must
correctly enable the DUMPSTYLE system parameter to enable the bugcheck code
to write the system dump file to an alternate device.
The following sections describe the requirements for DOSD
on Alpha, I64, and VAX systems.
DOSD Requirements on Alpha and I64 Systems On Alpha and I64 systems, DOSD has the following requirements:
The dump device directory structure
must resemble the current system disk structure. The [SYSn.SYSEXE]SYSDUMP.DMP file will reside there, with the
same boot time system root. Use AUTOGEN to create this file. In the MODPARAMS.DAT file,
the following symbol prompts AUTOGEN to create the file:
DUMPFILE_DEVICE = "$nnn$ddcuuuu"
You can enter a list of devices.
The dump disk must have an ODS-2 or ODS-5 file structure.
The dump device cannot be part of a volume set.
Although not a requirement, HP recommends
that you mount the dump device during system startup. If the dump
device is mounted, it can be accessed by CLUE and AUTOGEN and for
the analysis of crash dumps. For best results, include the MOUNT
command in SYS$MANAGER:SYCONFIG.COM.
For the Crash Log Utility Extractor (CLUE) to support
DOSD, you must define the logical name CLUE$DOSD_DEVICE to point
to the dump file to be analyzed after a system crash. For instructions, refer
to
Using SDA CLUE Commands to Analyze Crash Dump Files (Alpha and I64).
The dump device cannot be part of a shadow set unless
it is also the system device and the master member of the shadow
set.
On Alpha systems, use the following format to specify
the dump device environment variable DUMP_DEV at the console prompt:>>> SET DUMP_DEV device-name[,...]
On DEC 3000 series systems, the following restrictions
on the use of the DUMP_DEV environment variable exist:
This variable is not preserved across
system power failures because DEC 3000 series systems do not have
enough nonvolatile RAM to save the contents of the file. You must reset
the DUMP_DEV variable after a power failure. (DUMP_DEV is preserved
across all other types of restarts and bootstraps, however.)
You cannot clear DUMP_DEV (except by power-cycling
the system).
You must use console firmware Version 6.0 or greater
because earlier versions do not provide support for DUMP_DEV.
On some CPU types, you can enter only one device; on other
CPU types, you can enter a list of devices. The list can include
various alternate paths to the system disk and the dump disk.
On I64 systems, use the OpenVMS I64 Boot Manager
(BOOT_OPTIONS.COM) utility to specify the dump device environment
variable DUMP_DEV at the OpenVMS DCL prompt: $@SYS$MANAGER:BOOT_OPTIONS Alternatively, you can use the EFI for OpenVMS (I64 only)
VMS_SET utility to specify the dump device environment variable
DUMP_DEV at the EFI console prompt:
Shell> FSn:\EFI\VMS\VMS_SET DUMP_DEV device-name[,...] (where: FSn: is any bootable FAT file-structured partition that includes the VMS_SET utility)
Refer to the next section.
By specifying an alternate path with DUMP_DEV, the
disk can fail over to the alternate path when the system is running.
If the system crashes subsequently, the bugcheck code can use the
alternate path by referring to the contents of DUMP_DEV.
When you enter a list of devices, however, paths
to the system disk must come last.
You can designate the dump device on I64 systems by using
either of the following:
The
Boot Manager Utility, BOOT_OPTIONS.COM
The EFI utilities command
VMS_SET.
HP recommends that you use the use the OpenVMS I64 Boot
Manager Utility. (Use of the utility is optional for other devices
but mandatory for Fibre Channel devices.) For more information
on this utility, refer to the
HP OpenVMS
System Manager's Manual, Volume 1: Essentials.
To designate the dump device with the DUMP_DEV environment
variable from the OpenVMS DCL prompt, follow these steps:
At the
DCL prompt, enter the following command to invoke the OpenVMS I64
Boot Manager utility: $ @SYS$MANAGER:BOOT_OPTIONS.COM
The utility starts by displaying
the main menu. Set the utility to operate on the Dump Device Options list
by entering D at the prompt:
Enter your choice: D Sample output from adding an entry to the Dump Options
list follows:
OpenVMS I64 Boot Manager Dump Options List Management Utilities
(1) ADD an entry to the Dump Options list
(2) DISPLAY the Dump Options list
(3) REMOVE an entry from the Dump Options list
(4) MOVE the position of an entry in the Dump Options list
(B) Set to operate on the Boot Device Options list
(D) Set to operate on the Dump Device Options list
(G) Set to operate on the Debug Device Options list
(E) EXIT from the Boot Manager utility
You can also enter Ctrl-Y at any time to abort this utility.
While using this utility, you can change a response
by typing the up-arrow (^) as many times as you
need to. To end the program and return to the DCL prompt, enter
Ctrl/Y.
To designate the dump device
on the DUMP_DEV environment variable, option, enter 1 at following
prompt:
Enter your choice: 1
The utility prompts you for
the device name. Enter the device name of the DOSD device, as in
the following example, in which the dump device is multipath fibre
device DGA1:
Enter the device name (Enter "?" for a list of devices): $1$DGA1 efi$bcfg: $1$DGA1 (VMS_DUMP_DEV_01) Option successfully added efi$bcfg: $1$DGA1 (VMS_DUMP_DEV_02) Option successfully added efi$bcfg: $1$DGA1 (VMS_DUMP_DEV_03) Option successfully added
Repeat steps 3 to 4 to add
additional DUMP_DEV devices.
When you have successfully
added all DUMP_DEV options, exit from the utility by entering E
at the following prompt:
Enter your choice: E
Reboot the system and refer
to the section "Enabling DOSD on Alpha and I64 Systems."
Finally, enable the DOSD bit of the DUMPSTYLE system parameter
by setting bit 2. For example, enter the value of 4 at the SYSBOOT> prompt to designate an uncompressed physical dump
to an alternate disk with minimal console output:
SYSBOOT> SET DUMPSTYLE 4
The HP OpenVMS System Management Utilities Reference Manual
and online help contain
details about the DUMPSTYLE system parameter.
The error log dump file is always created
on the system disk so that error log buffers can be restored when
the system is rebooted. This file is not affected by setting the
DUMPSTYLE system parameter or the DUMP_DEV environmental variable.
The system chooses the first valid device that it finds in
the list as the dump device. Therefore, the dump disk path entries
must appear before the system disk entries in the list.
On Alpha systems, the number of devices that can be included
in DUMP_DEV is limited. This limit varies from platform to platform,
and it also depends on the device configuration. Some platforms
allow only a single device; others allow a list. Systems that allow
a list of devices limit the length of the list to 256 bytes in the
internal format that the console subsystem uses. This length provides
space for 4 entries if SCSI or CI-based disks are used, and 8 to
9 entries if fibre-channel disks are used.
On I64 systems, up to 99 devices can be included in DUMP_DEV,
regardless of platform or device configuration.
DOSD Requirements on VAX Systems On VAX systems, DOSD has the following requirements:
The system must be connected directly
to, and must boot from, CI controllers.
The dump device must physically connect to the same
two HSx CI controllers as the boot device. These two controllers
must be connected through the same CI star coupler.
The dump device directory structure must resemble
the current system disk structure. The [SYSn.SYSEXE]SYSDUMP.DMP file will reside there, with the
same boot time system root. Use AUTOGEN to create this file. In the MODPARAMS.DAT file,
the following symbol prompts AUTOGEN to create the file:
DUMPFILE_DEVICE = "$nnn$ddcuuuu"
You can list only one device.
The volume label can be up to 12 characters long.
The ASCII string DOSD_DUMP must be part of this volume label. For
example, valid volume labels are DOSD_DUMP, DOSD_DUMP_12, 12_DOSD_DUMP. The
label is read and retained in a memory boot data structure.
The dump device cannot be part of a volume set. HP strongly
recommends that the dump device also not be part of a shadow set.
The dump device cannot be MSCP unit zero (0); only
units 1 to 4095 (1--FFF) are supported. You can designate the dump device as follows:
On VAX 7000 configurations, by using
bits 16 through 27 of the DUMPSTYLE system parameter. Note that
the DUMP_DEV environment variable that is provided on VAX 7000 configurations
is not used by OpenVMS VAX.
On configurations other than the VAX 7000, by using
bits 16 through 27 of register 3 (R3). You can use this portion
of the register to specify the dump device.
The HP OpenVMS System Management Utilities Reference Manual
and online help contain
details about the DUMPSTYLE system parameter..
To restore error log buffers when the system is rebooted
after a system crash, the error logs must be saved on the system
disk. For this purpose, AUTOGEN creates a SYSDUMP.DMP file on the
system disk; the file is large enough to contain the maximum size
of error log buffers.
HP OpenVMS System Manager's Manual, Volume 2:... 
Managing Page, Swap, and Dump Files
