HP-UX Shared Memory Extensions

[Alzhy]

http://www.software.hp.com/portal/swdepot/displayProductInfo.do?productNumber=ShmemExt

This enhancement supposedly allows a 4X (four-fold) increase in number of Shared Memory Segments in concurrent usage.

Looks to me VM hogs like Oracle and JAVA apps wil benefit the most - but are there sites out there that are actually using this and saw the benefits?

DBA's, etc.. do later Oracle 9/10 documentation point to this package/enhancement as a requirement?

[RAC_1]

I was completely unware that something like this exists. Just going to documents now. Hope I put it on few servers and try it.

Anil

[Stephen Keane]

I see this is for 64-bit HPUX, does that mean it will/won't work for 32-apps running on 64-bit HP-UX?

[Don Morris_1]

It is targeted at the 64-bit kernel, the applications can be either 32 or 64-bit. The 32-bit kernel doesn't get the product because you're unlikely to have meaningful segments if you've carved up shared address space into more than 8,192 chunks. Just didn't seem likely.

[Deoncia Grayson_1]

I have Oracle 10 G loaded on one our hp servers here and ShmemEst is not a requierment for 10 G.

[Steve Lewis]

For servers with huge memory.

Way back when, we in database land were told to minimize the number of shared memory segments on HP-UX systems because of performance limitations in the PA-RISC cpu (only 1 fixed register SR6 controls shared memory). i.e. few big ones are far better than lots of small ones.

This should have all changed with Itanium 2 and may have changed with PA-RISC 2.0W, see
http://docs.hp.com/en/92432-90012/ch02s02.html?btnNext=next%A0%BB

and

http://docs.hp.com/en/92432-90012/ch03s01.html?btnNext=next%A0%BB

Comments and pointers, experts?

[Alzhy]

So Steve - do you think this will have a beneficial impact to 64-bit Oracle implementations if the enhancement statement:

"This enhancement supposedly allows a 4X (four-fold) increase in number of Shared Memory Segments in concurrent usage."

is true?

Has anyone from DBA land asked Oracle if they're aware of this HP_UX enhancements and whether it is a recommended upgrade?

[Don Morris_1]

Nelson - I don't believe Oracle performance recommends creating many small segments, which is what you'd require to hit the shmmni barrier. The Shared Memory Extensions product raises that barrier, allowing more segments to be in existence on the system at once. So if you haven't set shmmni to the maximum (8192) or if you have but your usage isn't anywhere near the maximum, all you'll really get out of the product is some tunable man pages [which granted, I think are nice to have on the system]. You aren't going to need it otherwise.

[Steve Lewis]

Nelson,

Not unless you have about 2000 instances(!), which would blow me away if anyone told me that they had either managed it or intended to.

Its just as Don said, it cures a limitation for enormous unpartitioned servers that have tens of thousands of concurrent processes, or users and require thousands of segments.

I don't think it would apply to databases so much as proprietary software.

ipcs -ma will list your segments. Count them and compare with your kernel settings.

Steve