Re: Keeping an Oracle 8.1.7 SGA in Physical Memory on Solaris 8

You are right, i was forgetting that it had changed in solaris 2.8, but what i said does apply to 2.6 and 2.7, and locking the shared memory in core still applies if you wish to do it.

cheers

Pete

In article <9mo234$9eu$1_at_news-int.gatech.edu>, jsc3_at_dontspamme.havoc.gtf .gatech.edu writes
>In comp.sys.sun.admin Pete Finnigan <pete_at_peterfinnigan.demon.co.uk> alleged:
>
>-> If you are looking to lock shared memory i take it you are having paging
>-> issues. Check vmstat and search on google or whatever to read about
>-> priority paging and what are real page in's and outs.
>
>-> You should also look at the "priority paging" mechanism used in solaris.
>
>-> add the parameter priority_paging=1 to your /etc/system This will stop
>-> the kernel grabbing all the free kernel memory.
>
>According to the "Solaris Tunable Parameters Reference Manual", you
>don't want to turn on priority paging if you are running Solaris 8:
>
>"We recommend that all tuning of the VM system be removed from /etc/system.
> Run with the default settings and determine if it is necessary to adjust
> any of these parameters. Do not enable priority_paging or adjust cachefree.
> These are no longer needed, although still present in the kernel.
> Manipulating them will almost certainly result in performance degradation
> when the page scanner runs."
>
>This is also mentioned prominently in the Release Notes, in the "Upgrade
>Issues" section:
>
>----------------------------------------------------------------------------
>Priority Paging Is Not Needed With the New Solaris 8 Caching Architecture
>
>The Solaris 8 operating environment introduces a new file system caching
>architecture, which subsumes the Solaris 7 Priority Paging functionality.
>You should not set the system variable priority_paging in the Solaris 8
>operating environment, and you should remove the variable from the
>/etc/system file when systems are upgraded to the Solaris 8 operating
>environment.
>
>The new caching architecture removes most of the pressure on the virtual
>memory system that resulted from file system activity. As a result, the new
>caching architecture changes the dynamics of the memory paging statistics,
>which makes observing system memory characteristics simpler. However,
>several of the statistics report significantly different values. You should
>consider these differences when analyzing memory behavior or setting
>performance monitoring thresholds. The most notable differences are:
>
> The number of page reclaims is higher, which you should
> consider normal operation during heavy file system activity.
>
> The amount of free memory is higher because the free memory
> count now includes a large component of the file system cache.
>
> Scan rates are almost zero unless there is a shortage of
> system-wide available memory. Scanning is no longer used to
> replace the free list during normal file system I/O.
>
>----------------------------------------------------------------------------
>
>So, if you are running Solaris 2.6 or 7, by all means turn on
>priority paging, but don't use it with Solaris 8.
>

-- 
Pete Finnigan
IT Security Consultant
PenTest Limited

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