Re: What is SPIN_COUNT?

In article <rp1399-1007951245540001_at_m12cim15.sps.mot.com>, rp1399_at_email.sps.mot.com (Steve Lemme) writes:
> In article <3tkslj$f5e_at_earth.superlink.net>, "William J. George"
> <wjgeorge_at_attmail.com> wrote:
>
> > Our group recently noticed that SPIN_COUNT was set to 1 on our development
> > machine and 2000 on our production machine. What is it? Is it a derived
> > value? Where do I find documentation for these parameters?
> >
> From what I understand Spin Count is now a hidden Oracle _parameter.
> In my Oracle tuning class we were told to remove that documented item from
> the text, and that ORacle would direct us if we needed to use that
> parameter.
> All I know, anyone else?
>
> Steve Lemme
> Motorola
>
> --
> When you are in it up to your ears....
> Keep your mouth shut!
> rp1399_at_email.sps.mot.com

On multiprocessor machies, like HP9000, Sparc 1000 etc the SPIN_LOCK concept is used. For example a block of disk space can be locked by a process and another process needs the same block. Instead of returning back to the process which requested the new lock immediatly telling the block is locked by somebody else, the process SPINS around for sometime to see the device is available for lock by the process.

If my understanding is right the SPIN_LOCK (called Mutexes in Solaris) is Operating system specific and is not available on all the OSes (at leat a year back). Also SPIN_LOCK is not necessarily for DISKS, it more for Semaphores and other UNIX internal specific operations.

SPIN_COUNT is a tunable parameter (based on application) for the delay to get hold of the lock or semaphore.

This was my understanding from an HP/Oracle expert. If somebody wants to clarify this or continue this thread please do so.

Prabhakar

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------------------------Prabhakar Kandasamy-------------------------------------
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