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Kernel Modification with Memory Added

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Steven Chen_1
Super Advisor

Kernel Modification with Memory Added


I have 1G memory on K260 of hpux11i running Oracle 8i now. 1G more memory will be added and therefore Oracle SGA will be modified too.

I would like to know that on hpux level if any kernel parameters need to to modified so that 2G memory can be used (to overcome kernel fence?).

It will be very appreciated if someone can help.

I would attach a concurrent kernel configuration file for your inspection. First thing jump to my mind is the maxdsiz.

Thanks a lot.

Jeff Schussele
Honored Contributor

Re: Kernel Modification with Memory Added

Hi Steven,

I don't see any kernel params that MUST be changed, but my caveat would be to make sure that swap *at least* is on a one-to-one ratio with memory.
And you already have swap_mem_on at 1 so that's alright.
You'll need to watch the system - particularly Oracle performance & the max*siz & shm* usage to determine if you'll need to tune these after the upgrade & Oracle SGA mod.
Also watch mem/swap usage closely.
Use sar over a broad time range across all normal Oracle usage scenarios if possible.

PERSEVERANCE -- Remember, whatever does not kill you only makes you stronger!
John Payne_2
Honored Contributor

Re: Kernel Modification with Memory Added


One thing to remember when adding memory is that dbc_max_pct and dbc_min_pct are percentages of memory. By adding another 1GB increment, if you do not change these values, your file system buffer cache will go from a 50MB-150MB range to a 100MB-300MB range. That is not necessarily bad, but if you do not want your buffer cache that big for an Oracle database machine, you need to lower the percentages.

It becomes a bigger problem when people have bigger percentages and add more memory...

Hope it helps.

nancy rippey
Trusted Contributor

Re: Kernel Modification with Memory Added

You will probably want to increase your swap if you are adding memory. Along with this you would want to increase maxswapchunks.

This (in conjunction with some other parameters) sets the maximum amount of swap space configurable on the system. Maxswapchunks should be set to support sufficient swap space to accommodate all swap anticipated. Also remember, swap space, once configured, is made available for paging (at boot) by specifying it in the file /etc/fstab (/etc/checklist on 9.X). The maximum swap space limit calculated in bytes is: (maxswapchunks * swchunk * DEV_BSIZE). We recommend this parameter be set to 4096.

Hope this helps


Steven Chen_1
Super Advisor

Re: Kernel Modification with Memory Added

Thanks all for the help.

So we don't have to do anything on maxdsiz, semmni, semmns, shmmni, shmmax....?