1. HP Unix Professions Webcast October 2007
HP-UX Swap and Dump Unleashed By Unix/Linux Apprentice with 26 Years of Experience
Dusan Baljevic
Sydney, Australia

2. Why This Document? * Frequent “abuse” of good design principles.
A “friend in need is a friend indeed” – why standard swap/dump design fails in real scenarios.
Everyone has different opinion – why not help system administrators and architects stop implementing bad practices.
Especially important on large-RAM servers.
Based on 26-year practical experiences in Unix/Linux.
* I will use “paging device” to describe “swap”. Both mean the same in this context.

3. This Document is Not: A replacement for HP’s official statements.
A written manual to learn HP-UX and its design principles in detail.
Glorified personal experience to prove that I “know best” (rather the opposite).

4. HP-UX Current Official Recommendations* - Part 1
Use the following guidelines when configuring swap logical
volumes:
Interleave device swap areas for better performance.
Two swap areas on different disks perform better than one swap area with the equivalent amount of space. This configuration allows interleaved swapping, which means the swap areas are written to concurrently, thus enhancing performance.
When using LVM, set up secondary swap areas within logical volumes that are on different disks using lvextend.
If you have only one disk and must increase swap space, try to move the primary swap area to a larger contiguous region.
* “HP-UX System Administrator's Guide: Logical Volume Management HP-UX 11i Version 3”

5. HP-UX Current Official Recommendations* - Part 2
Similar-sized device swap areas work best. Device swap areas must have similar sizes for best performance. Otherwise, when all space in the smaller device swap area is used, only the larger swap area is available, making interleaving impossible.
By default, primary swap is located on the same disk as the root file system. The kernel configuration file contains the configuration information for primary swap.
If you are using logical volumes as secondary swap, allocate the secondary swap to reside on a disk other than the root disk for better performance.
Disable mirror consistency checking for swap mirrored primary swap device (no need to recover after a failure).
Use Priority 0 device swap to bypass swap on root disk.
* “HP-UX System Administrator's Guide: Logical Volume Management HP-UX 11i Version 3”

6. HP-UX How Much Swap is Enough?
Every admin and architect has a different opinion.
Traditional views typically use formula:
SWAP = 1 or 2 x RAM
Some old designs and applications required even 3 x RAM (or more).
Old HP-UX releases had serious issue with (now obsolete) kernel parameter swapmem_on (see next slide).

7. HP-UX How Much Dump is Enough?* - Part 1
The vast majority of problems are found in the kernel area. Only
rarely do the program data areas need to be examined, even more
rarely, the shared memory areas, and virtually never the buffer/file
cache and shared libraries.
If a full crash dump is taken, the total space needed with be as
high as RAM (and a bit more).
By compressed dump overall time taken will be reduced by 1/3 as
well as the disk space required should also get reduced by at least
1/3 for default selection of page classes (usually the default page
class selection utilizes around 20% of the memory).
I have seen customers using the following formulas for crash dump device sizing:
Crash for 32-bit system => 2^32 = 4 GB
Crash for 64-bit system => 2^64 = 8 GB

8. HP-UX How Much Dump is Enough? – Part 2
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE no, by default kernel code pages
USTACK yes, by default user process stacks
FSDATA yes, by default file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
1:0x :0x /dev/vg00/lvol2
# getconf PAGESIZE
4096

9. With Pseudoswap (swapmem_on=1) Without Pseudoswap (swapmem_on=0)
[Module Title]
HP-UX Pseudoswap
Pseudoswap allows the kernel to treat a portion of physical memory as if it is swap space in order to satisfy the swap reservation policy. Pseudo-swap is enabled by default in all current versions of HP-UX and is removed as kernel parameter in11i v3 (swapmem_on).
I have 2GB of swap and 8GB of available memory. Can I start a 4GB process on
an idle server?
With Pseudoswap (swapmem_on=1)
Yes!
2GB Device Swap + 6GB Pseudo Swap (75% 8GB)
8GB Reservable Swap
Without Pseudoswap (swapmem_on=0)
No!
2GB Device Swap
+ 0GB Pseudo Swap
2GB Reservable Swap
[Rev. # or date] – © 2008 Hewlett-Packard Development Company, L.P.

10. Example of an Application Swap Requirements
Please see SAP note for a detailed explanation of swap sizing and pseudo-swap.
In general device swap configurations of 1.5 or 2 x RAM have proven appropriate for the majority of SAP installations. The recommendation is to set device swap to 2 x RAM (minimum 20 GB).
Please refer to SAP note for a detailed explanation of swap requirements on a per SAP instance basis.

11. Basics of Crash Dumps
* Courtesy of HP document “Crash Dumps”, Nov 2004
Prior to HP-UX 11.0, one of the first user space tasks in the boot process
was running savecore (now obsolete), which would check for a crash
dump and, if found, copy it from the dump device(s) to the file system.
This same program had many other features used by system
administrators after the system was up.
In HP-UX release 11i v1 and later releases, savecrash(1M) and
crashconf(1M) handle boot-time tasks and post-boot tasks, respectively.
The savecrash(1M) command runs at boot time and exports raw data
from dump areas to /var/adm/crash (by default); it preserves any and all
crash-related information which could be lost as system activity
continues. It has many options, which may be set in
/etc/rc.config.d/savecrash.
On servers with large amount of RAM, savecrash can take
significant amount of time!

12. Bad Example of Swap Design
# /usr/sbin/swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev % /dev/vg00/lvol2
dev % /dev/vg00/swap1
dev % /dev/vg00/swap2
dev % /dev/vg00/swap3
reserve
memory %
total %
This is a copy of swapinfo(1M) results taken on a mission-critical SD32 vPar.
It was not taken to “find” the culprit but to highlight the fact that even
engineers can make very wrong decisions (at least the good news is that
vg00 has eight physical volumes):
# /usr/sbin/lvdisplay -v /dev/vg00/lvol2
--- Logical volumes ---
LV Name /dev/vg00/lvol2
VG Name /dev/vg00
LV Permission read/write
LV Status available/syncd
Mirror copies
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes)
Current LE
Allocated PE
Stripes
Stripe Size (Kbytes)
Bad block off
Allocation strict/contiguous
IO Timeout (Seconds) default
--- Distribution of logical volume ---
PV Name LE on PV PE on PV
/dev/dsk/c0t0d
/dev/dsk/c2t0d
# /usr/sbin/lvdisplay -v /dev/vg00/swap1
LV Name /dev/vg00/swap1
/dev/dsk/c0t2d
/dev/dsk/c2t2d
# /usr/sbin/lvdisplay -v /dev/vg00/swap2
LV Name /dev/vg00/swap2
/dev/dsk/c0t4d
/dev/dsk/c2t4d
# /usr/sbin/lvdisplay -v /dev/vg00/swap3
LV Name /dev/vg00/swap3
/dev/dsk/c0t6d
/dev/dsk/c2t6d

13. HP-UX Maximum Swap Swap space in the kernel is managed using
'chunks' of physical device space. These chunks
contain one or more (usually more) pages of
memory, but provide another layer of indexing
(similar to inodes in file systems) to keep the global
swap table relatively small, as opposed to a large
table indexed by swap page.
swchunk controls the size in physical disk blocks
(which are defined as 1 KB) for each chunk.

14. Maximum Swap on HP-UX Before 11i V3
The total bytes of swap space manageable by the
system on HP-UX 11i older releases is:
swchunk x 1KB x 16384
where16384 is the system maximum number of
swap chunks in the swap table, as defined by
kernel parameter maxswapchunks.
swchunk has allowed values between 2048 and
65536 blocks.

15. Maximum Swap on HP-UX 11i V3
The total bytes of swap space manageable by the
system on HP-UX 11i v3 is:
swchunk x 1KB x

16. Dump Terms [Module Title]
[Course Title]
Dump unit A thread of execution during dump. A dump unit requires its own set of CPUs, dump devices, and other resources, which are non-overlapping with other dump units.
Reentrancy Capability of a dump driver to issue multiple I/Os simultaneously, one I/O per HBA port, during dump.
Concurrency Capability of a dump driver to issue multiple I/Os simultaneously per HBA port, during dump. In HP-UX 11i v3 this capability means that the driver can issue I/Os simultaneously to multiple devices under a given HBA port, one I/O per device.
Parallel Dump HP-UX 11i v3 dump infrastructure which enables the parallelism features.
Reentrant HBA port or device An HBA port or device controlled by a reentrant driver.
Concurrent HBA port or device An HBA port or device controlled by a concurrent driver.
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

17. [Module Title]
Dump Unit - Part 1 *
[Course Title]
A Dump Unit is an independent sequential unit of execution within the dump process.
Each dump unit is assigned an exclusive subset of the system resources needed to perform the dump, including CPUs, a portion of the physical memory to be dumped, and a subset of the configured dump devices. The dump infrastructure in HP-UX 11i v3 automatically partitions system resources at dump time into dump units.
Each dump unit operates sequentially.
Parallelism is achieved by multiple dump units executing in parallel.
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

18. [Module Title]
Dump Unit - Part 2 *
[Course Title]
A dump device cannot be shared across multiple dump units.
Multiple “reentrant devices” can be accessed in parallel only if the devices are configured through separate HBA ports. Thus all “reentrant devices” on the same HBA port will be assigned to a single dump unit.
Each “concurrent device” can be accessed in parallel. Each can therefore be assigned to a separate dump unit, even if configured through a single HBA port.
Multiple dump volumes on a single physical volume will not allow for parallelism. Parallelism at dump time can only be achieved across multiple physical devices (LUNs).
Logical volumes configured as dump devices: all logical volumes which reside on the same physical device (LUN) are assigned to the same dump unit.
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

19. Dump Options Overview Selective Compressed Parallel (concurrent)
[Module Title]
Dump Options Overview
[Course Title]
Selective
Based on classes/uses of memory
Compressed
>=5 CPUs per dump unit
Mixed compressed/non-compressed images
Parallel (concurrent)
Faster dump with multiple “monarchs”
Influenced by memory availability and dump devices
HP Integrity Servers only
Live dump
Crashdump a live system without forced shutdown or panic
System stays up, running & stable
Offline analysis of system
Memory image -> file
Extra load during this save
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

20. [Module Title]
Dump Parallelism
[Course Title]
I/O support during dump is provided via dump drivers, and each configured
dump driver reports its parallelism capabilities to the dump infrastructure:
Legacy: new parallelism feature is not supported
Reentrant: supports parallelism per HBA port
Concurrent: supports parallelism per dump device
These requirements can be distilled into the following formulas for calculating
the number of dump units that can be achieved:
CPU Parallelism = (number of CPUs available at dump time) / (1 or 5, depending on whether or not compression is enabled)
Device Parallelism = (number of reentrant dump HBA ports) + (number of concurrent dump devices) + (1 if there are any legacy dump devices)
Number of Dump Units = Minimum (CPU Parallelism, Device Parallelism)
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

21. Dump Driver Parallelism Capability
[Module Title]
Dump Driver Parallelism Capability
[Course Title]
Examples of HP-provided dump drivers on HP-UX 11.31:
fcd Concurrent
td, mpt, c8xx, ciss, sasd, fclp Reentrant
# crashconf -l
DEVICE LOGICAL VOL NAME LUNPATH HANDLE *
1:0x :0x /dev/vg00/lvol /0/2/0/0/0/0/4/0/0/0.0x247000c0ffdb3fb9.0x
# ioscan -fNk | grep "40/0/2/0/0/0/0/4/0/0/0 "
fc /0/2/0/0/0/0/4/0/0/0 fclp CLAIMED INTERFACE HP AD PCIe Fibre Channel 2-port 4Gb FC/2-port 1000B-T Combo Adapter
* Take lunpath handle 40/0/2/0/0/0/0/4/0/0/0.0x247000c0ffdb3fb9.0x and
And remove everything to the RIGHT from the first “point” character:
40/0/2/0/0/0/0/4/0/0/0
Then, use this value (along with a blank space after it) to run ioscan
command:
# ioscan -fNk | grep "40/0/2/0/0/0/0/4/0/0/0 “ |
there is a blank space before the quotes
The dump driver will be listed in the resulting line. In the above example, it is fclp.
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

22. Dump Driver Capability
[Module Title]
Dump Driver Capability
[Course Title]
# scsimgr get_attr -a capability -H 40/0/2/0/0/0/0/4/0/0/0 SCSI ATTRIBUTES FOR CONTROLLER : 40/0/2/0/0/0/0/4/0/0/0 name = capability current = "Boot Dump" default = saved =
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

23. Uncompressed vs. Compressed Dump – One Dump Device *
[Module Title]
Uncompressed vs. Compressed Dump – One Dump Device *
[Course Title]
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

24. Uncompressed vs. Compressed Dump – Three Dump Devices *
[Module Title]
Uncompressed vs. Compressed Dump – Three Dump Devices *
[Course Title]
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

25. Uncompressed vs. Compressed Dump – Legacy Devices *
[Module Title]
Uncompressed vs. Compressed Dump – Legacy Devices *
[Course Title]
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

26. Uncompressed Dump – Reentrant Devices *
[Module Title]
Uncompressed Dump – Reentrant Devices *
[Course Title]
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

27. Uncompressed vs. Compressed Dump – Complex Example *
[Module Title]
Uncompressed vs. Compressed Dump – Complex Example *
[Course Title]
* Courtesy of “HP-UX 11i v3 Crash Dump Improvements”, 2007
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

28. Compressed Dump Configuration
[Module Title]
Compressed Dump Configuration
[Course Title]
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE yes, forced kernel code pages
USTACK yes, by default user process stacks
FSDATA no, forced file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON # crashconf –c off to turn compression off until reboot
# crashconf –c on to turn compression on until reboot
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
3:0x :0x /dev/vg00/lvol2
3:0x :0x /dev/vg00/v3Dump
Dump device configuration mode is config_deprecated_mode.
Use crashconf -s option to change the mode.
# kctune dump_compress_on
Tunable Value Expression Changes
dump_compress_on Default Immed # crashconf –tc off to change tunable to 0
# kctune dump_compress_on=0
# crashconf –tc on to set tunable to 1
# kctune dump_compress_on=1
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

29. Compressed Dump Algorithm
[Module Title]
Compressed Dump Algorithm
[Course Title]
HP-UX uses one processor to do all disk writes and four processors for compression.
The algorithm for compression is Lempel–Ziv–Welch (LZW).
LZW is a universal lossless data compression algorithm, simple to implement, and has the potential for very high throughput in hardware implementations.
One of the reasons for selecting LZW:
HP has a license to use it, and
It achieves pretty good compression ratio.
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

30. Concurrent Dump Configuration
[Module Title]
Concurrent Dump Configuration
[Course Title]
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE yes, forced kernel code pages
USTACK yes, by default user process stacks
FSDATA no, forced file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON
Dump Parallel: ON # crashconf –p off to turn concurrent dump off until reboot
# crashconf –p on to turn concurrent dump on until reboot
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
3:0x :0x /dev/vg00/lvol2
3:0x :0x /dev/vg00/v3Dump
Dump device configuration mode is config_deprecated_mode.
Use crashconf -s option to change the mode.
# kctune dump_concurrent_on
Tunable Value Expression Changes
dump_concurrent_on Immed # crashconf –tp off to change tunable to 0
# kctune dump_concurrent_on=0
# crashconf –tp on to set tunable to 1
# kctune dump_concurrent_on=1
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

31. HP-UX Kernel Parameters alwaysdump and dontdump
[Module Title]
HP-UX Kernel Parameters alwaysdump and dontdump
[Course Title]
On rare occasions, the system may panic before crashconf(1M) is run
during the boot process. On those occasions, the configuration can be
set using the alwaysdump and dontdump tunables.
# kctune -v -q alwaysdump
Tunable alwaysdump
Description Bitmap of memory page classes to include in a crash dump
Module dump
Current Value [Default]
Value at Next Boot 1024
Value at Last Boot 0
Default Value
Can Change Immediately or at Next Boot
* The integer value should be the sum of the integer values for the included classes as follows
(maximum value 1024):
UNUSED : Unused pages
USERPG : User pages
BCACHE : Buffer cache
KCODE : Kernel text pages
USTACK : Process stack
FSDATA : File-system Metadata
KDDATA : Kernel dynamic data
KSDATA : Kernel static data
SUPERPG : Unused superpage pool
[Rev. # or date] – © 2007 Hewlett-Packard Development Company, L.P.

32. HP-UX Typical Crash Dump Configuration
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE no, by default kernel code pages
USTACK yes, by default user process stacks
FSDATA yes, by default file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
1:0x :0x /dev/vg00/lvol2
Dump device configuration mode is config_deprecated_mode. Use crashconf -s option to
change the mode.

33. HP-UX Savecrash Locking
Dump devices are often used as paging devices (primary swap is one
such example). If savecrash determines that a dump device is already
enabled for paging, and that paging activity has already taken place on
that device, a warning message will indicate that the dump may be invalid.
If a dump device has not already been enabled for paging, savecrash
prevents paging from being enabled to the device by creating the file
/var/adm/crash/.savecrash.LCK.
swapon does not enable the device for paging if the device is locked in
/var/adm/crash/.savecrash.LCK. As savecrash finishes saving
the image from each dump device, it updates the
/var/adm/crash/.savecrash.LCK file and optionally executes
swapon to enable paging on the device.

34. HP-UX Dump Device in Non-Root VGs
As of HP-UX we have the possibility to configure
additional dump devices online (without the need of a
reboot. These dump LVs must not be configured using
lvlnboot –d but with crashconf(1M).
We are no longer restricted to choose a dump LV from
the root VG only. The configuration of such dump
devices is similar to the configuration of secondary
swap devices.

35. Example of Classical Swap/Dump Design on HP-UX
Potential Issues
If shortage of RAM, boot disks experience severe I/O performance problems due to swap usage.
If more RAM is added, not easy to resize primary swap (contiguous blocks).
Long reboot due to savecrash(1M) export to /var/adm/crash.
More swap added in other VGs, often different in size than primary.
Waste of large amount of disk space for swap.
Primary PV Alternate PV
/stand
/stand
Primary swap/
dump
/stand
/stand
Primary swap/
Dump mirror
Other LVs
Other LVs
RAID-1 for Boot disk
32 GB RAM
Swap = 1 or 2 x RAM
Swap/dump shared

36. Example of Different Swap/Dump Design on HP-UX with Internal Boot Disks *
Primary PV Alternate PV
SAN-based LUNs or LVs
* Although I did not use term “Better” (instead, term “Different” was chosen),
I strongly believe this is really a better design.
** In fact, I prefer not to have large amount of swap initially and only through testing
evaluate the need to have something like 1xRAM in total.
/stand
/stand
Secondary swap
Secondary swap
Primary swap
Primary swap mirror
Other LVs
Other LVs
Dump area
Dump area
Dump areas set up on different
LUNs or PVs in non-root VGs
(dump PVs are NEVER RAID-1
in LVM)
RAID-1 for Boot disks
32 GB RAM
Primary Swap = 4-8 GB
Total Swap = 1 x RAM **
Swap NOT shared with dump

37. Example of Different Swap/Dump Design on HP-UX with SAN Boot Disk *
Boot PV
SAN-based LUNs or LVs
/stand
Secondary swap
Secondary swap
Primary swap
Other LVs
* Although I did not use term “Better” (instead, term “Different” was chosen),
I strongly believe this is really a better design.
** In fact, I prefer not to have large amount of swap initially and only through testing
evaluate the need to have something like 1xRAM in total.
Dump area
Dump area
Dump areas set up on different
LUNs or PVs in non-root VGs
(dump PVs are NEVER RAID-1
in LVM)
32 GB RAM
Primary Swap = 4-8 GB
Total Swap = 1 x RAM **
Swap NOT shared with dump

38. HP-UX Persistent Dump Devices – Part 1
Persistent Dump Devices are those that are configured automatically after a reboot. Persistent dump devices information is maintained in the kernel registry services, (KRS, see krs(5)).
To mark the dump devices as persistent, there are two configuration modes available.
config_crashconf_mode
In this mode crashconf(1M) and crashconf(2) are the only mechanisms available to mark dump devices as persistent. Logical volumes marked for dump using lvlnboot(1M) or vxvmboot(1M) and devices marked in /stand/system for dump will be ignored during boot-up. This is the preferred method for dump device configuration and will be used from this HP-UX release onwards. This mode can be enabled using the crashconf -s option. VxVM stores extent information of persistent dump logical volumes in lif(4). Up to ten VxVM logical volumes can be marked persistent. The logical volumes which are not part of the root volume group cannot be configured as persistent dump devices.

39. HP-UX Persistent Dump Devices – Part 2
config_deprecated_mode
The logical volumes marked for dump using lvlnboot(1M) or vxvmboot(1M) and devices marked in /stand/system for dump will be configured as dump devices during boot-up. Devices marked as persistent, using crashconf -s, will be ignored during boot-up. Marking devices using lvlnboot(1M), vxvmboot(1M), and /stand/system will be obsolete in the next HP-UX release. This mode is deprecated on HP-UX and will be obsolete in the next HP-UX release. This is the default mode for dump and can be enabled using the crashconf -o option.

40. HP-UX Dump Devices and Bad Block Relocation
From HP-UX release onwards, the LVM bad block relocation feature is obsolete. However, for compatibility reasons the value is maintained as a logical volume attribute.
If BBRA is not disabled when dump device is created, HP-UX complains about “unsupported disk layout”.
Hence, the correct procedure to create a dump device in LVM is:
# lvcreate -C y -r n -L n dump2 /dev/vgdump

41. HP-UX Crashconf Fails with Unsupported Disk Layout Error - VxVM
The volume dumpvol was added to the /etc/fstab file and crashconf was issued to increase the total dump
area but crashconf failed with the message below:
/dev/vx/dsk/rootdg/dumpvol: error: unsupported disk layout
The crashconf error is due to the dump area not being contiguous:
# vxprint -g rootdg -ht  
v dumpvol ENABLED ACTIVE SELECT swap
pl dumpvol-01 dumpvol ENABLED ACTIVE CONCAT RW
sd rootdisk01-07 dumpvol-01 rootdisk c1t4d0 ENA
sd rootdisk01-17 dumpvol-01 rootdisk c1t4d0 ENA
The dumpvol volume has two areas on c1t4d0. The first is rootdisk01-07 which starts at and is
kb in size and the second is rootdisk01-17 which starts at and is also kb in
size. The volume dumpvol needs to be contiguous so the last kb should be reduced from
dumpvol. To reduce dumpvol:
# vxassist shrinkby dumpvol

42. HP-UX Crashconf Fails with Unsupported Disk Layout Error - LVM
/dev/vg01/lvswap: error: unsupported disk layout
# lvdisplay /dev/vg01/lvswap
....
Bad block on
Allocation strict
Dump is required to be contiguous and have bad block reallocation
turned off:
# lvchange -C y -r n /dev/vg01/lvswap

43. HP-UX VxVM Dump Device Creation* – Part 1
With Volume Manager 5.0 on HP-UX 11.31, to initialize the disk, must use
vxdisksetup -ifB <disk> command, vxdiskadm is unable to
initialize the disk correctly for use with crashconf. Please note that CDS
diskgroups are not affected. Those can still be initialized via vxdiskadm.
# vxdisk list
DEVICE TYPE DISK GROUP STATUS
c2t0d0s2 auto:none online invalid
c2t1d0s2 auto:hpdisk rootdisk01 rootdg online
# vxdisk -f init c2t0d0s2 format=hpdisk
# vxdg init dumpdg c2t0d0s2 cds=off
# vxassist -g dumpdg -U swap make dumpvol 3g *

44. HP-UX VxVM Dump Device Creation – Part 2
# crashconf -s /dev/vx/dsk/dumpdg/dumpvol
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE no, by default kernel code pages
USTACK yes, by default user process stacks
FSDATA yes, by default file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
3:0x :0x /dev/vx/dsk/rootdg/swapvol
3:0x :0x414ad8 /dev/vx/dsk/dumpdg/dumpvol

45. HP-UX Better Swap and Dump Design – Part 1
Set up primary swap between 4 and 8 GB ONLY, no matter how large the RAM is!
Primary swap device should not be NOT SHARED with dump.
Initially, set up primary swap only. In the pre-production testing, verify if that is enough and avoid creating other swap areas unless absolutely necessary.
Secondary swaps (if you need to have them!) are created as 4-8 GB LUNs (could be LVs in LVM or Plexes in VxVM) on SAN (if practicable). Ensure that secondary swaps match the size of primary swap. That way, if server ever needs to use swap, the performance of swap devices will be excellent and boot disk I/O will never “suffer”.
If primary swap is left at 4-8 GB, then allocate separate dump areas in other volume groups to match the size of physical memory if compression is disabled or not possible (due to lack of available CPUs), or less if compression is enabled and possible.

46. HP-UX Better Swap and Dump Design – Part 2
Disable savecrash(1M) at boot (/etc/rc.config.d/savecrash):
SAVECRASH=0
If you do it, make sure not to forget to run savecrash(1M) after the reboot.
Dedicated dump device will not shorten the time required to write from memory to the dump volume during the crash, but will shorten the reboot time. This is because the crash image are not at risk being overwritten by page or swap activity and savecrash(1M) can run in background to save the crash files into the crash dump directory.
If the dump device is also configured as one of the swap devices, the device cannot be enabled for paging until savecrash(1M) has finished saving the image from the device to the crash dump directory. Therefore, the boot time will be longer if savecrash is run in foreground. This extra time will be even greater if vPars are configured because multiple dump images may have to be saved.

47. HP-UX Better Swap and Dump Design – Part 3
When dump and swap areas are separated, there is no need to save the crash images at boot time. Therefore, savecrash(1M) at (re)boot can be disabled!
The reduction in reboot time achieved by configuring a separate dump device (close to 50% over classical design with savecrash running in foreground) is likely to provide a worthwhile return on investment when system availability is a priority.
Using identical sizes and types of dump devices and HBAs in the dump configuration is one way to avoid inequalities in dump speeds or times across the dump units. This tends to produce more predictable results and better overall parallelism.

48. HP-UX Better Swap and Dump Design – Part 4
It is recommended that shared swap and dump devices or volumes not be used with parallel dump. Using a shared swap/dump device can significantly increase the subsequent reboot time because such devices result in swap being disabled while saving the corresponding dump data (for example, in /var/adm/crash).
Avoid file system swap altogether if possible.
Set priorities of SAN-based secondary swaps to lower value than the primary swap (and let it be identical value across all secondary swaps). That way, if there is a serious shortage of RAM, swap will perform as “perfectly striped” volume.

49. HP-UX Better Swap and Dump Design – Part 5
If compressed dumps are required, ensure that there are five CPUs per each dump unit.
Set up multiple dump units on SAN (non-root volume groups), and enable parallel dumps. Note that, currently, the logical volumes which are not part of the root volume group in LVM cannot be configured as persistent dump devices. * However, non-root data group with VxVM can be used for persistent dump devices. **
* From the latest HP-UX crashconf patch:
PHCO_ crashconf(1M) cumulative patch
[..]
Defect ( QX:QXCR )
crashconf (1M) man page does not contain the information
"The logical volumes which are not part of the root volume
group cannot be configured as persistent dump devices".
Resolution:
crashconf (1M) man page is updated with the below information
group in LVM cannot be configured as persistent dump devices".
** An example for VxVM:
# crashconf -v Crash dump configuration has been changed since boot. CLASS PAGES INCLUDED IN DUMP DESCRIPTION UNUSED no, by default unused pages USERPG no, by default user process pages BCACHE no, by default buffer cache pages KCODE no, by default kernel code pages USTACK 1004 yes, by default user process stacks FSDATA 14 yes, by default file system metadata KDDATA yes, by default kernel dynamic data KSDATA 7955 yes, by default kernel static data SUPERPG 4744 no, by default unused kernel super pages Total pages on system: Total pages included in dump: Dump compressed: ON Dump Parallel: ON DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME :0x00000c :0x /dev/vx/dsk/rootdg/swapvol 1:0x :0x2892b8 /dev/vx/dsk/secdumpswapdg/secdumpswapvol Persistent dump device list: /dev/vx/dsk/secdumpswapdg/secdumpswapvol

50. HP-UX Better Swap and Dump Design – Part 6
For a kernel dump, the usual requirement: Kernel text/static data Kernel dynamic data in use User-space kernel thread stacks (UAREA) Kernel dynamic memory, which is free-and-cached (Super Page Pool), is only needed when there is a problem in the SPP itself (pretty rare). User data is very rarely needed (in addition, most users do not want HP support reading their application private data for security reasons (classified data, customer sensitive, and so on). The default configuration for crashconf is good enough for most situations.
If enough disk space available or no other constraints imposed, you might enable all crash classes in dumps (check crashdump(1M)).

51. Guidelines for Selecting Device Swap
[Module Title]
Guidelines for Selecting Device Swap
[Course Title]
Two swap areas on different disks are better than one single swap area
Only configure one swap area per disk
Device swap areas should be of similar size
Consider the speed of the disks
Swap LV
Swap LV
Swap LV
Swap LV
Swap LV
No!
Yes!
[Rev. # or date] – © 2008 Hewlett-Packard Development Company, L.P.

52. HP-UX Post-crash Manual Dump Export
If the dump was not saved completely due to lack of space in the crash directory you have the possibility to save the dump again. The -r option (resave) need to be included when this is not the first time that savecrash runs.
# savecrash -v [-r] <crash directory>
There is also the possibility to save the dump directly to a tape:
# savecrash -v [-r] -t <tapedevice>

53. HP-UX Manual Dump Export from a Specific Dump Device
To manually extract the dump, type either the persistent DSF or the legacy
DSF of the whole disk along with the offset:
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
3:0x :0x /dev/vg00/lvol2
3:0x :0x02000b /dev/vg01/dump_3
3:0x :0x02000a /dev/vg01/dump_2
3:0x :0x /dev/vg01/dump_1
# savecrash -D /dev/rdisk/disk4 -O r -v . or   
# savecrash -D /dev/rdsk/c2t1d0 -O r -v .

54. Swapoff Available with HP-UX 11.31.
The swapoff(1M) command disables swapping on the specified swap device(s) for the current boot. The term swap refers to an obsolete implementation of virtual memory; HP-UX actually implements virtual memory by way of paging rather than swapping. This command and others retain names derived from swap for historical reasons.
Does not remove swap device from /etc/fstab.
Will not be successful if amount of swap is needed, for example, reserve space as reported by swapinfo(1M).
Example:
# /usr/sbin/swapoff /dev/vg00/lvol2

55. Swapoff – Real Life Example – Part 1
Remove primary swap and move it into another volume group. To remove the primary swap, we need to ensure that the new swap device has at least enough space that “reserve” requires. Otherwise, swapoff(1M) command will fail!
# lvcreate -C y –r n -L n lvswap2 /dev/vgswap
# swapon -f /dev/vgswap/lvswap2
# swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev % /dev/vg00/lvol2
dev % /dev/vgswap/lvswap2
reserve
memory %
total %

56. Swapoff – Real Life Example – Part 2
Remove primary swap on-line:
# swapoff /dev/vg00/lvol2
# lvrmboot -s vg00
# swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev % /dev/vgswap/lvswap2
reserve
memory %
total %

57. Swapoff – Real Life Example – Part 3
Add line into /etc/fstab for the new primary swap and reboot the server:
/dev/vg00/lvol3 / vxfs delaylog 0 1
/dev/vg00/lvol1 /stand vxfs tranflush 0 1
/dev/vg00/lvol4 /home vxfs delaylog 0 2
/dev/vg00/lvol5 /tmp vxfs delaylog 0 2
/dev/vg00/lvol6 /usr vxfs delaylog 0 2
/dev/vg00/lvol7 /var vxfs delaylog 0 2
/dev/vg00/lvol8 /var/tmp vxfs delaylog 0 2
#/dev/vg00/lvdump3 / dump defaults 0 0
/dev/vgswap/lvswap2 / swap defaults 0 0

58. Swapoff – Real Life Example – Part 4
After the reboot, check swap status and confirm that non-root volume is now the primary swap:
# swapinfo -tm
Mb Mb Mb PCT START/ Mb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev % /dev/vgswap/lvswap2
reserve
memory %
total %

59. Swapoff – Real Life Example – Part 5
However, because we did not initialize the disk in vgswap with “-B” option, it does not contain the Boot Area, and cannot be added with “lvlnboot -s /dev/vgswap/lvswap2”. As a result, this is reported:
# lvlnboot -v
Boot Definitions for Volume Group /dev/vg00:
Physical Volumes belonging in Root Volume Group:
/dev/disk/disk6_p2 -- Boot Disk
Boot: lvol1 on: /dev/disk/disk6_p2
Root: lvol3 on: /dev/disk/disk6_p2
No Swap Logical Volume configured
No Dump Logical Volume configured

60. Swapoff – Real Life Example – Part 6
We still have one persistent dump device, which is NOT listed in /etc/fstab*:
# crashconf -v
Crash dump configuration has been changed since boot. 
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE no, by default kernel code pages
USTACK yes, by default user process stacks
FSDATA yes, by default file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON 
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
1:0x :0x /dev/vg00/lvdump3
Persistent dump device list:
/dev/vg00/lvdump3
* Crash dump will happily use this persistent device in volume group vg00!

61. Crash Dump – Two Dump Unit Example – Part 1
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE no, by default kernel code pages
USTACK yes, by default user process stacks
FSDATA yes, by default file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: OFF 
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
1:0x :0x /dev/vgroot/lvol2
1:0x :0x /dev/vgdump/dump2
1:0x :0x /dev/vgdump/dump3
Persistent dump device list:
/dev/vgroot/lvol2
* Crash dump will happily use this persistent device in volume group vg00!

62. Crash Dump – Two Dump Unit Example – Part 2
*** A system crash has occurred. (See the above messages for details.)
*** The system is now preparing to dump physical memory to disk, for use
*** in debugging the crash.
*** The dump will be a SELECTIVE dump with
compression OFF and concurrency ON: of megabytes.
Primary Dump Header Location :
Device details:
Major number: 0x1f Minor number: 0xb0000
Offset:
*** Dumping: 100% complete (2320 of 2320 MB)
time: 84 seconds, Number of Dump units: 2
* Crash dump will happily use this persistent device in volume group vg00!

63. Crash Dump Without Primary Swap, No Persistent Devices, and No Dump Devices in /etc/fstab
Console logs at boot time after a crash:
No crash dump devices defined.
Persistent dump device list is empty.
All subsequent crashes will fail to collect data into dump volumes:
Swap device table: (start & size given in 512-byte blocks)
entry 0 - auto-configured on root device; ignored - no room
WARNING: No swap device configured, so dump cannot be defaulted to
primary swap.
WARNING: No dump devices are configured. Dump is disabled.
Message buffer contents after system crash:
These messages are the contents of msgbuf, which should have been saved
In the dump. They are output to the console, as the dump was not taken.

64. How to Set the Dump Order for Saving System Crash – Part 1
The current dump configuration first saves the crash to dump2 , dump1 , then to lvol2:
# crashconf Crash dump configuration is changed after boot:
CLASS          PAGES  INCLUDED IN DUMP  DESCRIPTION          UNUSED        570458  no,  by default   unused pages USERPG        136677  no,  by default   user process pages BCACHE         10426  no,  by default   buffer cache pages KCODE           7764  yes, forced       kernel code pages USTACK          1172  yes, by default   user process stacks FSDATA             8  yes, by default   file system metadata KDDATA        192353  yes, by default   kernel dynamic data KSDATA          3641  yes, by default   kernel static data SUPERPG       120995  no,  by default   unused kernel super pages Total pages on system:            Total pages included in dump:        Dump compressed:    ON DEVICE        OFFSET(kB)   SIZE (kB)  LOGICAL VOL.  NAME              31:0x021000      924532        64:0x000002  /dev/vg00/lvol2  31:0x021000             64:0x00000a  /dev/vg00/dump1  31:0x021000             64:0x00000b  /dev/vg00/dump2                                                        

65. How to Set the Dump Order for Saving System Crash – Part 2
SOLUTION:
/etc/fstab does not list vg00/lvol2 , because it is the default dump volume.
    /dev/vg00/dump1 ... dump defaults 0 0   /dev/vg00/dump2 ... dump defaults 0 0
Edit /etc/fstab file for the new order of the dump LVs. The order of the dump LVs is opposite of the placement in the file, and vg00/lvol2 needs to be listed last to be used as the first dump lvol.
    New listing of dump area's in /etc/fstab           /dev/vg00/dump2 ... dump defaults 0 0    # last dump area used     /dev/vg00/dump1 ... dump defaults 0 0    # second dump area used     /dev/vg00/lvol2 ... dump defaults 0 0    # first dump area used
Edit /etc/rc.config.d/crashconf :
    CRASHCONF_ENABLED=1     CRASHCONF_READ_FSTAB=1     CRASHCONF_REPLACE=1

66. How to Set the Dump Order for Saving System Crash – Part 3
Put the new dump configuration in place (when a crash is saved, the first dump area is lvol2 followed by dump1 , then by dump2 ):
# /sbin/rc1.d/S080crashconf start
Check the new configuration:
# crashconf
CLASS          PAGES  INCLUDED IN DUMP  DESCRIPTION          UNUSED        169224  no,  by default   unused pages USERPG        500811  no,  by default   user process pages BCACHE         10412  no,  by default   buffer cache pages KCODE           7764  yes, forced       kernel code pages USTACK          1218  yes, by default   user process stacks FSDATA            20  yes, by default   file system metadata KDDATA        241200  yes, by default   kernel dynamic data KSDATA          3641  yes, by default   kernel static data SUPERPG       109204  no,  by default   unused kernel super pages Total pages on system:            Total pages included in dump:     Dump compressed:    ON DEVICE        OFFSET(kB)   SIZE (kB)  LOGICAL VOL.  NAME              31:0x021000              64:0x00000b  /dev/vg00/dump2  31:0x021000              64:0x00000a  /dev/vg00/dump1  31:0x021000      924532         64:0x000002  /dev/vg00/lvol2                                                        

67. Example of Distributed Swap Design
# /usr/sbin/swapinfo –t
Kb Kb Kb PCT START/ Kb
TYPE AVAIL USED FREE USED LIMIT RESERVE PRI NAME
dev % /dev/vgroot/lvol2 (4096MB)
dev % /dev/vgswap1/swap1 (4096MB)
dev % /dev/vgswap2/swap2 (4096MB)
reserve
memory %
I am also very passionate about naming volume groups and
logical volumes in a meaningful manner. *
* The following standard is recommended when creating volume groups
and logical volumes:
Environment One-letter Three-letter
Production P PRD
Backup (interim for tape backup) B BCK
Development D DEV
User Acceptance Testing U UAT
Training T TRN
Production Support A PSP
Pre-Production S PPD
System Test V SYS
Proof of Concept/Prototype C POC
System Integration Test I SIT
Operational Acceptance Test O OAT
Regression Test R REG
Data Migration M DAM
Enterprise Application Integration E EAI
For example, first production volume group for Oracle database is
called vgoraP01.

68. Paginglist Command # /usr/sam/lbin/paginglist
/dev/vg00/lvol2|dev| |4.0 GB|0|0.0 KB| |4.0 GB|0%|0|-|1|no|now|
reserve|reserve|0|0.0 KB| |1.9 GB| | `KB||0||0|no|now|
total|total| |4.0 GB| |1.9 GB| |2.1 GB|48%|0|0|0|no|now|

69. Patch Servers Regularly
Some of HP-UX dump patches:
PHKL_41977: HANG OTHER crashconf(1M) hangs when trying to configure
more than 32 dump devices. This patch fix allows to configure a logical volume
as primary swap and, provide support to FCD and FCLP NPIV (N_Port ID
Virtualization) enablement.
PHKL_41257: HANG During MCA handling, the system hangs in the process
of generating a crashdump.
PHKL_39740: OTHER System fails to dump memory into dump devices.
PHKL_38628: PANIC P
HKL_38414: ABORT If in the kernel, base page size is configured greater than
4k, dump may get aborted prematurely and affect debugging of crash.

70. Add Timestamps to RC scripts – Part 1
If there are RC startup problems, /etc/rc.log is usually the first place we need to check. The output from RC scripts can be found there, but rc.log has no timestamp for each RC script.
In order to let rc.log has timestamp for each RC script, put date command into each RC script, but this is not a good choice because there are so many files to updates. A better option is to set /sbin/rc.utils. The rc.utils script intercepts the output of RC scripts and logs it to /etc/rc.log , we can make it log timestamps as well.   
Backup /sbin/rc.utils before you make changes, ensure permissions unchanged:
# cp -p /sbin/rc.utils /sbin/rc.utils.bak
Edit /sbin/rc.utils , find the two lines echo >> $LOGFILE , (one is under routine do_screen_mode , the other is under do_line_mode ), insert a new line:
date >> $LOGFILE

71. Add Timestamps to RC scripts – Part 2
/etc/rc.log reports:
Thu Aug 18 12:22:28 EST 2011
Configure system crash dumps
Output from "/sbin/rc1.d/S080crashconf start":
EXIT CODE: 0
...
Thu Aug 18 12:22:33 EST 2011
Save system crash dump if needed
Output from "/sbin/rc1.d/S440savecrash start":
savecrash directory not set; defaulting to: /var/adm/crash
*EXIT: parse_args
ENTER: open_source
ENTER: read_header
ENTER: get_hdr_loc
*EXIT: get_hdr_loc
savecrash: Finished Reading Header From: device : /dev/rdsk/c11t0d0 offset:

72. Crash Dump Scenarios – Part 1
If there are no crash dump devices on HP-UX, by design, server will default to primary swap for saving crash dumps!
Persistent crash dump devices must be in root volume group in LVM, but can be in any data group in VxVM (Symantec documentation confirms it too).
If the crash dump devices are not persistent, and they are not listed in /etc/fstab, and swap is not in root volume group, HP-UX will happily use non-persistent dump devices from other volume groups AS LONG as they are defined in the currently running kernel configuration (check with crashconf(1M) command).

73. Crash Dump Scenarios – Part 2
To make non-persistent dump devices enabled permanently, they need to be added into /etc/fstab and “switched on” via crashconf(1M) command and/or /etc/rc.config.d/crashconf BEFORE crash happens. Otherwise, if there is no fall-back to primary swap, crash dump will FAIL.
A dump can be saved to both non-persistent and persistent dump devices*.
If there are persistent crash dump devices (they must be in root volume group in LVM, but can be in any data group in VxVM), they will be used for saving crash dumps even if they are not listed in /etc/fstab.
* When running HP-UX 11.31, can a dump be saved to a non persistent dump device?
The system dump configuration shown in the following example has a non-persistent (/dev/vgdump/dump_1 ) and a persistent (/dev/vg00/lvol2 ) dump device.
# crashconf -v
Crash dump configuration has been changed since boot.
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
UNUSED no, by default unused pages
USERPG no, by default user process pages
BCACHE no, by default buffer cache pages
KCODE no, by default kernel code pages
USTACK yes, by default user process stacks
FSDATA yes, by default file system metadata
KDDATA yes, by default kernel dynamic data
KSDATA yes, by default kernel static data
SUPERPG no, by default unused kernel super pages
Total pages on system:
Total pages included in dump:
Dump compressed: ON
Dump Parallel: ON
DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
3:0x :0x /dev/vg00/lvol2
3:0x :0x /dev/vgdump/dump_1
Persistent dump device list: 
/dev/vg00/lvol2
ANSWER:
A dump can be saved to both non-persistent (/dev/vgdump/dump_1 ) and persistent dump devices.
For the previous configuration, the first 2.4 GB is saved to /dev/vgdump/dump_1 , and the next 18.8 GB will be saved to /dev/vg00/lvol2 as follows:
 INIT occurs.
INIT: make crash event table.
INIT: Waiting for processors to save state.
INIT: Invoking callbacks.
Calling function e a4a0 for Shutdown State 9 type 0x10 INIT, IIP:0xe bd3a10 IFA:0xe c68808
INIT: Executing platform dependent procedures.
INIT: Begin crashdump.
I 0 pfn 0x1 pages 0x9f
I 1 pfn 0x100 pages 0x3e776
I 2 pfn 0x3eb8e pages 0x2ec
I 3 pfn 0x3fc00 pages 0x228
I 4 pfn 0x pages 0x80000
I 5 pfn 0x pages 0xbeffc
I 6 pfn 0x40feffe pages 0xbe0
I 7 pfn 0x40ffc48 pages 0x1bc
I 8 pfn 0x40ffe7e pages 0x14c
*** Not enough CPUS for a compressed dump ***
*** A system crash has occurred. (See the above messages for details.)
*** The system is now preparing to dump physical memory to disk, for use
*** in debugging the crash.
*** The dump will be a SELECTIVE dump with
compression OFF and concurrency ON: 894 of 6125 megabytes.
*** To change this dump type, press any key within 10 seconds.
*** Proceeding with selective dump, with compression off and concurrency on.
Primary Dump Header Location :
Device details:
Major number: 31 Minor number:0x20000
Offset: <--- Note the offset is of /dev/vgdump/dump_1   
*** The dump may be aborted at any time by pressing ESC.
*** Dumping: 100% complete (894 of 894 MB)
time: 36 seconds, Number of Dump units: 1
INIT[4]: OS_INIT ends. Resetting the system.
The system will then begin self test and reboot as normal.

74. HP Unix Professions Webcast October 2007
Thank You!
Dusan Baljevic
Sydney, Australia