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memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

SACHIN_9
Occasional Visitor

memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

hi
I want to knwo following :
1) If hp unix 11.0 (64) bit restricts mutliple 32 bit oracle instacnes to share only max. of 1.75 GB total memory ?
2) if yes, then how do we configure Hp unix 11.0 (64 bit) so that it can allow multiple instacnes to have more than 1.75 GB ( I read somehwere on can configure Windows so this restrictions will not remain so...)
7 REPLIES
Helen French
Honored Contributor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

Hi Sachin,

The shmmax 'Single shared memory segment' is limited to 1 GB (0x40000000) on a 32-bit HP-UX 11.0 system. When running under the 64-bit operating system, shmmax is limited to 1 TB (0x10000000000).

The maximum shared memory accessible (all segments/quadrants) is limited to 2.75 GB on 32-bit, and 4 TB on 64-bit HP-UX systems. SAM's online help incorrectly states that the shmmax maximum value is 1.75 GB (0x70000000).

HTH,
Shiju


Life is a promise, fulfill it!
SACHIN_9
Occasional Visitor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

hi
we are planning for more than one instances ( 32 bit) in a HP box ( 64 bit ,11.0), and i was told that sum of all Oracle SGAs can not exceeed 1.75 GB is it true?
Dennis J Robinson
Frequent Advisor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

Sachin,

On a 32bit system the maximum size of a shared memory segment is 1GB (0x40000000).

The maximum amount of shared memory systemwide is 1.75GB.

By linking the executables as EXEC_MAGIC and chatr'ing as SHMEM_MAGIC 2.75GB systemwide is possible.

If you run memory windows, it will be possible for each Oracle instance on the server to have its own global area of 1GB with .75GB in memory quadrant 4 to be used for shared libraries and the such.

The question is why do you insist on running the 32bit Oracle on 64bit HP-UX.
You know the drill
SACHIN_9
Occasional Visitor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

hi
we have tested our appliation using oracle 32 bit version also i referrred few articles and were suggesting that 32 bit version of oracle is more stable compared to 64 bit and patch availibility is more in 32 bit version
a) How to configure Hp unix 11.0 with memory as windows enabled ?
b) If there are 2 oracle instacnes, physical memory is 5 GB and memory option is enabled can we have both SGA sizes as 2GB each?
bye
sachin
Patrick Wallek
Honored Contributor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

Here is a white paper on Memory Windows in 11.0:
http://docs.hp.com/hpux/onlinedocs/os/memwn1_4.pdf

Here are a some document IDs from the TKB that discuss Memory Windows as well:

A5489578C
HPUXWP19
KBAN00000306
Bill Hassell
Honored Contributor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

All 32bit applications share the same addressing restriction *and* the same shared memory address range. Thus multiple instances of Oracle will be crippled by not having enough shared memory (which will become very fragmented as processes start and stop (including commercial backup tools).

Only a 64bit program is essentially unrestricted in the amount of shared memory that can be requested.

For 32bit Oracle, you'll need 5 separate memory windows, thus allowing as much as 1.75 Gb of SGA (Oracle will request SGA in 1 Gb segments) for each instance. Memory windows are not shared with other IPC uses so it will not become fragmented. Note that if each instance requests the maximum SGA possible in a window, you may exceed your installed RAM and significant paging to/from swap may take place.


Bill Hassell, sysadmin
Alexander M. Ermes
Honored Contributor

Re: memory more than 1.75 GB for HP unix 11.0 (64 bit) with oracle 8i (32 bit)

Hi there.
Bill's answer is correct.
That is why we changed to Oracle 8 64-bit.
No problems at all. Production downtime last year 2.5 hrs according to hardware failures on a V2500.
Rgds
Alexander M. Ermes
.. and all these memories are going to vanish like tears in the rain! final words from Rutger Hauer in "Blade Runner"