Re: Maximize Number of Instances on RHEL 7.9

Many DBAs forego the use of AMM, and opt for ASMM, or even manual memory management.

The manual method was found to be useful in 11g, don't think I have used in from 12c on, usually using ASMM.

On Sun, Oct 8, 2023, 8:55 AM <asterger_at_earthlink.net> wrote:

> Something I should have stated up front, all of these small instances
> are using AMM which is incompatible with Linux hugepages.
>
> Any other thing I have overlooked?
>
> -- Alan
>
> On 10/7/2023 9:44 PM, Jared Still wrote:
> > Something to keep in mind about recommendations: ask yourself why the
> > recommendation was made.
> >
> > As Mladen mentioned, hugepages are not swapped out.
> >
> > The load on the CPU is greatly reduced for memory operations.
> >
> > Standard memory pagesize on Linux is 4k.
> >
> > Run this cmd: getconf PAGESIZE
> > (I think that is correct)
> >
> > That reduces page lookups by 512x.
> >
> > With fewer addresses, the CPU TLB (Google it :) is more likely to
> > have it cached.
> >
> > I don't know why hugepages would not be recommended.
> >
> > Some OSs just do it automatically.
> >
> > On Sat, Oct 7, 2023, 10:32 AM <asterger_at_earthlink.net> wrote:
> >
> > Jared - Thanks for replying.
> >
> > From my research, hugepages was recommended for SGAs over 4G.
> > Most of
> > my SGAs are in the 1.2-3G range.
> >
> > Thanks,
> >
> > -- Alan
> >
> >
> > On 10/7/2023 12:40 PM, Jared Still wrote:
> > > One of the things I am curious about is why no hugepages?
> > >
> > > I'm not aware of hugepages being non-useful due to small SGA size.
> > >
> > > With so many instances I would think it rather a good feature to
> > employ.
> > >
> > >
> > > On Sat, Sep 2, 2023, 3:17 PM Alan Sterger
> > <asterger_at_earthlink.net> wrote:
> > >
> > > Hello,
> > >
> > > Looking for guidance in maximizing number of Oracle
> > instances on a
> > > RHEL
> > > 7.9 server for Dev/Val testing, not Production.
> > >
> > > We are running Oracle SE2 with threaded_execution and small
> SGAs
> > > therefore, not using server HugePages. Databases
> > > use_large_pages=false
> > > along with _ksmg_granule_size=4194304 (4M). Currently hosting
> 31
> > > instances, using memory_target with half of the instances set
> to
> > > 2560M,
> > > the other half at 1240M. Most are 19c, 6 at 12c.
> > >
> > > total used free shared buff/cache
> > > available
> > > Mem: 92G 10G 30G 35G
> > > 51G 45G
> > > Swap: 31G 0B 31G
> > >
> > > Assume I need to alter kernel parameters SHMMAX and SHMALL
> > from their
> > > defaults setting ~80% of the 92G for oracle databases.
> > >
> > > What can you add or suggest doing?
> > >
> > > Thanks,
> > >
> > > -- Alan
> > >
> > >
> > > --
> > > http://www.freelists.org/webpage/oracle-l
> > >
> > >
> >
>
>

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