Re: Kernel parameter recommendations for HP-UX 11.11 in regard to SGA size

From: joel garry <joel-garry_at_home.com>
Date: Tue, 05 Jun 2007 16:53:10 -0700
Message-ID: <1181087590.912542.265160@x35g2000prf.googlegroups.com>

On Jun 5, 2:39 pm, Swoop <s..._at_doesnotwork.com> wrote:
> sybrandb wrote:
> > On Jun 5, 12:01 pm, Swoop <s..._at_doesnotwork.com> wrote:
> >> I'm knew to HP-UX and was just after some advice in regards to some
> >> kernel parameters. I've done a fair bit of research but some of the
> >> things I've read seem to conflict and because lower versions of the OS
> >> have different settings and because the amount of RAM on the boxes (that
> >> they are configuring) differ it is hard to peg it down.
>
> >> For example, a metalink document recommends setting the system buffer
> >> cache to a maximum of 128M but it says this for a low amount of RAM,
> >> however, it doesn't specify what it means by low :(
>
> >> I'll be testing it out first on a test box.
>
> >> 2 processor box, HP-UX 11.11
> >> 4Gb RAM
> >> Running 9.2.0.8
> >> vxfs filesystem
> >> Running four databases (largest is 30Gb, others are 2Gb) as a pure
> >> database server
>
> >> Just wondering how others have configured the following parameters
>
> >> bufpages
> >> dbc_max_pct
> >> dbc_min_pct
> >> nbuf

On a 4 processor 8G system with 2 databases (one test) I have:

bufpages             0    (nbuf*2)
dbc_max_pct      50
dbc_min_pct        5   (see the kernel help for determining, once you
get to a steady state it doesn't matter so much)
nbuf                    0   "This parameter is for backwards

compatibility and should be set to zero because dynamic buffer cache is preferred."

>
> >> in regards to system buffer cache?
>
> > You need to configure the databas filesystems for directio, as Oracle
> > already has a buffer cache.
>
> Unfortunately I cannot do this at this time for reasons outside of my
> control :(

Sybrand has a way of being right, especially regarding coming into this century.

>
> > The above parameters are referring to the *O/S* buffer cache, which
> > you shouldn't use.
>
> The OS needs to have an appropriately sized buffer cache even if this is
> quite small. This is the main part of my question. What is an
> appropriate size with 4Gb RAM on a pure database server?
>
> > You need to read up the *platform specific* documentation for HP-UX
> > available onhttp://otn.oracle.com(tahiti.oracle.com only has generic
> > docs)
>
> I have read the platform specific data which did mention many kernel
> parameters but not the ones listed above :(

Oftentimes, if they aren't mentioned, you don't need to worry :-)

>
> > Four databases on 4 Gb RAM is a recipe for disaster.
>
> Unfortunately most companies live far from a perfect world and thus a
> DBA has to work with the resources that she/he currently has. In the
> role that the databases are being used for, 4Gb is adequate. Adequate
> being measured in user response time.

Watch out for pga_aggregate_target.

--
@home.com is bogus.
"After several years at one client site, I was still finding old
abandoned ORACLE_HOMES on servers I had never known existed." - Mark
Brinsmead

Received on Tue Jun 05 2007 - 18:53:10 CDT