| Dump space is one or a series of disk devices used to store a system crashdump . By default, HP-UX will configure a single dump device. The initial dump device is also configured as the primary swap device. Primary swap is a contiguous volume, and as such it is not easy to extend its size . Consequently, in order to configure additional dump space, we will need to configure additional dump devices that can be either individual disks or volumes (LVM or VxVM). If we are using volumes, the volumes do not need to be created in the root volume/disk group . Together with our initial dump device, they form our total dump space. If we are going to create a volume to act as a dump device, there is a criterion to which dump devices must adhere : If we don't follow this strict criterion, the volume will not be added to the list of dump devices. If the size of our crashdump exceeds the size of our configured dump space, it is time to configure additional dump devices. To add a device to the list of current dump devices, we use the crashconf command again. Here's an example using an LVM volume that doesn't match the strict criterion for the organization of a dump area:
root@hpeos003[] lvcreate -L 1000 -n dump2 /dev/vgora1 Logical volume "/dev/vgora1/dump2" has been successfully created with character device "/dev/vgora1/rdump2". Logical volume "/dev/vgora1/dump2" has been successfully extended. Volume Group configuration for /dev/vgora1 has been saved in /etc/lvmconf/vgora1.conf root@hpeos003[] crashconf /dev/vgora1/dump2 /dev/vgora1/dump2: error: unsupported disk layout root@hpeos003[]
We will have to remove the volume and recreate it using the appropriate options:
root@hpeos003[] lvremove /dev/vgora1/dump2 The logical volume "/dev/vgora1/dump2" is not empty; do you really want to delete the logical volume (y/n) : y Logical volume "/dev/vgora1/dump2" has been successfully removed. Volume Group configuration for /dev/vgora1 has been saved in /etc/lvmconf/vgora1.conf root@hpeos003[] lvcreate -L 1000 -n dump2 -C y -r n /dev/vgora1 Logical volume "/dev/vgora1/dump2" has been successfully created with character device "/dev/vgora1/rdump2". Logical volume "/dev/vgora1/dump2" has been successfully extended. Volume Group configuration for /dev/vgora1 has been saved in /etc/lvmconf/vgora1.conf root@hpeos003[] crashconf /dev/vgora1/dump2 root@hpeos003[] crashconf Crash dump configuration has been changed since boot. CLASS PAGES INCLUDED IN DUMP DESCRIPTION -------- ---------- ---------------- ------------------------------------- UNUSED 157473 no, by default unused pages USERPG 25075 no, by default user process pages BCACHE 35771 no, by default buffer cache pages KCODE 2581 yes, forced kernel code pages USTACK 839 yes, by default user process stacks FSDATA 205 yes, by default file system metadata KDDATA 26932 yes, by default kernel dynamic data KSDATA 13268 yes, by default kernel static data Total pages on system: 262144 Total pages included in dump: 43789 DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME ------------ ---------- ---------- ------------ ------------------------- 31:0x01f000 117600 2097152 64:0x000002 /dev/vg00/lvol2 31:0x001000 2255296 1024000 64:0x010005 /dev/vgora1/dump2 ---------- 3121152 root@hpeos003[]
Here's another example using a VxVM volume this time:
root@hpeos003[] vxassist -g ora1 make dump3 200M layout=contig root@hpeos003[] crashconf /dev/vx/dsk/ora1/dump3 root@hpeos003[] crashconf Crash dump configuration has been changed since boot. CLASS PAGES INCLUDED IN DUMP DESCRIPTION -------- ---------- ---------------- ------------------------------------- UNUSED 157383 no, by default unused pages USERPG 25174 no, by default user process pages BCACHE 35771 no, by default buffer cache pages KCODE 2581 yes, forced kernel code pages USTACK 843 yes, by default user process stacks FSDATA 209 yes, by default file system metadata KDDATA 26940 yes, by default kernel dynamic data KSDATA 13268 yes, by default kernel static data Total pages on system: 262144 Total pages included in dump: 43789 DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME ------------ ---------- ---------- ------------ ------------------------- 31:0x01f000 117600 2097152 64:0x000002 /dev/vg00/lvol2 31:0x001000 2255296 1024000 64:0x010005 /dev/vgora1/dump2 31:0x048000 7793120 204800 1:0x768f97 /dev/vx/dsk/ora1/dump3 ---------- 3325952 root@hpeos003[]
If we want these dump devices to be activated after a reboot, we need to add an appropriate entry to the /etc/fstab file:
root@hpeos003[] vi /etc/fstab ... /dev/vgora1/dump2 ... dump defaults 0 0 /dev/vx/dsk/ora1/dump3 ... dump defaults 0 0 root@hpeos003[]
There's one other issue regarding the size of our dump space. During the process of crashing, we are given the opportunity on the system console to perform a full dump of everything in memory. This is effectively an image of main memory written to the dump device(s). In order to perform a full dump, we would need to have enough dump space to accommodate an image that will be slightly (approximately 10 percent) bigger than the size of the RAM configured in our system. A full dump is seldom needed these days, but if requested by our local Response Center engineers , we may have to configure even more dump space/devices. Now we need to consider what happens after the system crashes. | 