how to set the size between dump and /var/adm/crash

[study unix]

Hello,
crashconf -v
CLASS PAGES INCLUDED IN DUMP DESCRIPTION
-------- ---------- ---------------- -------------------------------------
UNUSED 146910 no, by default unused pages
USERPG 39849 no, by default user process pages
BCACHE 26356 no, by default buffer cache pages
KCODE 2657 no, by default kernel code pages
USTACK 933 yes, by default user process stacks
FSDATA 153 yes, by default file system metadata
KDDATA 31661 yes, by default kernel dynamic data
KSDATA 13113 yes, by default kernel static data

Total pages on system: 261632
Total pages included in dump: 45860

DEVICE OFFSET(kB) SIZE (kB) LOGICAL VOL. NAME
------------ ---------- ---------- ------------ -------------------------
31:0x021000 1313632 4194304 64:0x000002 /dev/vg00/lvol2
----------
4194304

I analysis the correct dump size should be 229300KB (45860*4KB*1.25), but I want to know how much space is for /var/adm/crash, is the same size "229300kb" or other size after compressed, please kindly give my some suggestion!
Thanks in advance!

[pradeep m]

Hi,
There is no specific calculation to define the size of /var/adm/crash. It is advised to have enough free space under /var so that it can accommodate multiple crash dumps in case of server crash.

In case of server crash or panic, the entire Physical memory is dumped to the configured dump device during reboot, which in turn dumps to the local file system. (Default location: /var/adm/crash)

So the important thing to consider is to configure the dump device in accordance with the Total Page size to get the complete OS core dump.

Dump devices are volumes on the disk that are used to hold the entire memory image when the system crashes. The cumulative size of all specified dump devices has to be some MB larger than the amount of memory in order to hold the entire core.

So from your output,
>>>Total pages on system: 261632 (261632 x 4KB)
>>>Dump Device size = 4194304KB

The Condition are,
1. "Total pages size" should be equal or less than the "Total Dump size"
2. Make sure you have enough free space under /var/

Hope this information helps.

Regards,
Pradeep