Re: sga_max_size problem (Warning in alert log)

On 15 Maj, 15:06, "fitzjarr..._at_cox.net" <fitzjarr..._at_cox.net> wrote:
> On May 14, 4:59 pm, christianeriks..._at_vfemail.net wrote:
>
>
>
>
>
> > Hi!
>
> > I would be most grateful if anyone could explain in detail what's
> > going on here. We have a warning message in the alert log saying:
>
> > WARNING: EINVAL creating segment of size 0x0000000101400000
> > fix shm parameters in /etc/system or equivalent
>
> > and this hexadecimal value I find to be 4315938816 in decimal. Now the
> > question is why oracle tries to allocate this value because we have
> > set a smaller value in the spfile:
>
> > oracle_at_S0242169# grep sga_max_size /SSW/oracle/product/9.2.0.6.0/dbs/
> > spfiledw
> > *.sga_max_size=4294967296
>
> > which is the same value as in /etc/system
>
> > oracle_at_S0242169# grep shmmax /etc/system
> > set shmsys:shminfo_shmmax=4294967296
>
> > (and the system is indeed started with this value:
>
> > oracle_at_S0242169# sysdef | grep -i shmmax
> > 4294967296 max shared memory segment size (SHMMAX))
>
> > Despite the above the instance ends up with a larger memory allocation
> > than sga_max_size and shmmax:
>
> > oracle_at_S0242169# echo "show parameter sga_max_size" | sqlplus -s '/ as
> > sysdba'
>
> > NAME TYPE
> > VALUE
> > ------------------------------------ -----------
> > ----------------------------
> > sga_max_size big integer 4296515696
>
> > Why is that?
>
> > Can it have something to do with oracle rounding up it's memory
> > allocation to "a page boundary" as stated in the below qoute:
>
> > >Fromhttp://www.dba-oracle.com/t_shared_memory_ram_unix_errors.htm
>
> > 3) The size of the shared memory segment requested is invalid. In
> > this
> > case, EINVAL is returned by the system. This should be very rare
> > - however,
> > it is possible. This can occur if SHMMAX is not a mulitple of
> > page
> > size and Oracle is trying a multi-segment model. Remember that
> > Oracle
> > rounds its calculation of SHMMAX to a page boundary, so it may
> > have
> > rounded it up past the real SHMMAX! (Whether this is a bug is
> > debatable).
>
> > OS: Solaris 9 9/04 s9s_u7wos_09 SPARC
> > Oracle server: Oracle9i Enterprise Edition Release 9.2.0.6.0 - 64bit
> > Production
>
> > Regards Christian Eriksson
>
> Your SHMMAX value is set to 4 gig, and I doubt very seriously you'll
> have page boundary issues with that allocation. I'm expecting this is
> possibly a bug, fixed in a subsequent patch. You need to patch this
> installation to 9.2.0.8, test again, and if the problem persists
> contact Oracle Support.
>
> David Fitzjarrell- Dölj citerad text -
>
> - Visa citerad text -

Now oracle says this in the metalink SR we have opened: "... In cases where the SHMMAX is smaller than the SGA size, Oracle tries to fit the entire SGA into a single shared memory segment. ...".

Isn't it true that oracle tries to fit the entire SGA into a single shared memory segment also when the SHMMAX is larger or equal to the sgasize? Received on Mon May 21 2007 - 08:25:56 CDT