Dump - Core

AIX generates a system dump when a severe error occurs. A system dump creates a picture of the system's memory contents. If the AIXkernel crashes kernel data is written to the primary dump device. After a kernel crash AIX must be rebooted. During the next boot, thedump is copied into a dump directory (default is /var/adm/ras). The dump file name is vmcore.x (x indicates a number, e.g. vmcore.0)

When installing the operating system, the dump device is automatically configured. By default, the primary device is /dev/hd6, which is apaging logical volume, and the secondary device is /dev/sysdumpnull.

A rule of thumb is when a dump is created, it is about 1/4 of the size of real memory. The command "sysdumpdev -e" will also provide anestimate of the dump space needed for your machine. (Estimation can differ at times with high load, as kernel space is higher at thattime.)

When a system dump is occurring, the dump image is not written to disk in mirrored form. A dump to a mirrored lv results in aninconsistent dump and therefore, should be avoided. The logic behind this fact is that if the mirroring code itself were the cause of thesystem crash, then trusting the same code to handle the mirrored write would be pointless. Thus, mirroring a dump device is a waste ofresources and is not recommended.

Since the default dump device is the primary paging lv, you should create a separate dump lv, if you mirror your paging lv (which issuggested.)If a valid secondary dump device exists and the primary dump device cannot be reached, the secondary dump device will acceptthe dump information intended for the primary dump device.

IBM recommendation:All I can recommend you is to force a dump the next time the problem should occur. This will enable us to check which process was hangingor what caused the system to not respond any more. You can do this via the HMC using the following steps: Operations -> Restart -> DumpAs a general recommendation you should always force a dump if a system is hanging. There are only very few cases in which we candetermine the reason for a hanging system without having a dump available for analysis.

-------------------------------------------

Traditional vs Firmware-assisted dump:

Up to POWER5 only traditioanl dumps were available, and the introduction of the POWER6 processor-based systems allowed system dumps tobe firmware assisted. When performing a firmware-assisted dump, system memory is frozen and the partition rebooted, which allows a newinstance of the operating system to complete the dump.

Traditional dump: it is generated before partition is rebooted.(When system crashed, memory content is trying to be copied at that moment to dump device)

Firmware-assisted dump: it takes place when the partition is restarting.(When system crashed, memory is frozen, and by hypervisor (firmware) new memory space is allocated in RAM, and the contents of memory iscopied there. Then during reboot it is copied from this new memory area to the dump device.)

Firmware-assisted dump offers improved reliability over the traditional dump, by rebooting the partition and using a new kernel to dumpdata from the previous kernel crash.

When an administrator attempts to switch from a traditional to firmware-assisted system dump, system memory is checked against thefirmware-assisted system dump memory requirements. If these memory requirements are not met, then the "sysdumpdev -t" command outputreports the required minimum system memory to allow for firmware-assisted dump to be configured. Changing from traditional to firmware-assisted dump requires a reboot of the partition for the dump changes to take effect.

Firmware-assisted system dumps can be one of these types:

Selective memory dump: Selective memory dumps are triggered by or use of AIX instances that must be dumped.Full memory dump: The whole partition memory is dumped without any interaction with an AIX instance that is failing.

-------------------------------------------

Use the sysdumpdev command to query or change the primary or secondary dump devices. - Primary: usually used when you wish to save the dump data - Secondary: can be used to discard dump data (that is, /dev/sysdumpnull)

690,933PAGEVIEWS

ABOUT

FS

LV

Mirror Pool

PV

VG

FS - LVM

AIX History

Backup

Commands

CPU - Processes

Crontab - At

Date - Time

Devices

Dump - Core

Errpt - Diag - Alog -Syslogd

Firmware

IO - AIO, DIO, CIO

Memory - Pag.Space

ODM

Printing

SRC

Startup - Shutdown

System - Kernel

Tunables

User - Group

User Login

GENERAL

Appl. Monitor

Basics

Build - Configure

Clverify

Commands - Cases

Config too long

DARE - Snapshot

Disk Heartbeat

Storage - VG, NFS

HACMP - POWERHA

ASMI

HMC Basics - Console

HMC CLI

HMC/P7 InstallISD Basics

RMC

HMC - ISD

Basics - Devices,Routing

Basics - Protocol,Subnet

Basics - Vlan

Commands

Eth. Chan.

Ethernet Adapter

IVE - HEA

Netcd

NFS

RSH - RCP

Sendmail

SSH - SCP

SSH - X11

Telnet - FTP

NETWORK

Basics

Install

LPP Source

Machines

MKSYSB

Nimadm

SPOT

NIM

AIX for System Administrators http://aix4admins.blogspot.mx/2011/06/aix-generates-system-dump-w...

1 of 3 04/06/2013 16:43

Flags for sysdumpdev command: -l list the current dump destination -e estimates the size of the dump (in bytes) -p primary -s secondary -P make change permanent -C turns on compression -c turns off compression -L shows info about last dump -K turns on: alway allow system dump

sysdumpdev -P -p /dev/dumpdev change the primary dumpdevice permanently to /dev/dumpdev

root@aix1: /root # sysdumpdev -lprimary /dev/dumplvsecondary /dev/sysdumpnullcopy directory /var/adm/rasforced copy flag TRUEalways allow dump TRUE

Newer Post Older PostHome

Subscribe to: Post Comments (Atom)

Labels: GENERAL

errpt shows which program, if not:- use the strings command (for example: strings core | grep _=)- or the lquerypv command: (for example: lquerypv -h core 6b0 64)

man syscorepathsyscorepath -p /tmpsyscorepath -g

Comment as:

1 comment:

basanth February 13, 2013 at 6:51 PM

How to take the backups of SYSdump and Device?

Reply

Template images by Storman. Powered by Blogger.

AIX for System Administrators http://aix4admins.blogspot.mx/2011/06/aix-generates-system-dump-w...

3 of 3 04/06/2013 16:43