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sga_max_size problem (Warning in alert log)

From: <christianeriksson_at_vfemail.net>
Date: 14 May 2007 14:59:05 -0700
Message-ID: <1179179945.791800.20360@h2g2000hsg.googlegroups.com>


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:

>From http://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 Received on Mon May 14 2007 - 16:59:05 CDT

Original text of this message

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