I've tried to install IBM DB2 v11.5.5 followingthis manual. I've gotten to step 13 in Procedure section and I've got error, because I've installed v11.5.5. So I started db2prereqcheck program without parameters and got this error in section for v11.5.5:
Validating "ipcmni_extend kernel parameter " ... WARNING : Requirement not matched.
It's only requirement not matched.
I tried to google solution but got nowhere. I'm using Ubuntu 18.04.
1 Answer
Although it is only a warning, (and so can be ignored in many cases) it straightforward to make the change.
But there can be a slight performance penalty, so only enable this parameter if db2start forces you, or if you have more than 128GB of RAM and you know that your Db2 instances will consume more than the available default IPC resources.
If you are using all defaults for ubuntu 20.04 then here is one way to make the change (i.e. to set the parameter) permanently:
- become root
- take a backup of the text file
/etc/default/grub - edit
/etc/default/grubto alter the lineGRUB_CMDLINE_LINUX_DEFAULTto add the wordipcmni_extend - save the modified file
update-grubshutdown -r now- after reboot,
cat /proc/cmdlineto verifyipcmni_extendis present db2prereqcheckwill no longer show the warning.
Notes:
(1) If the kernel command-line parameter ipcmni_extend is not enabled or the system has less than 128 GB of RAM, this value is set to 32768 ( = left at default ).
(2) (RHEL advice) The ipcmni_extend parameter extends a number of unique System V Inter-process Communication (IPC) identifiers from the current maximum of 32 KB (15 bits) up to 16 MB (24 bits). As a result, users whose applications produce a lot of shared memory segments are able to create a stronger IPC identifier without exceeding the 32 KB limit.
(3) (RHEL advice) Note that in some cases using ipcmni_extend results in a small performance overhead and it should be used only if the applications need more than 32 KB of unique IPC identifier.
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