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List: hpux-admin
Subject: [HPADM] HP-UX Oracle/ Shared memory segment question
From: Simon Loewenthal <simon.loewenthal () tele2 ! com>
Date: 2009-12-29 12:23:42
Message-ID: OFC11FA41A.37C4A8A2-ONC125769B.00439D78-C125769B.004416D3 () tele2 ! com
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Dear all,
I read the article below about setting the shared memory for Oracle.
My knowledge of Oracle is poorly. Does the article imply that each
instance of of the pmon process should only have six shared memory
segments afore it runs out of protection keys?
What happens if there are two instances of pmon running on the server each
with six shared mem segments (12 in total) - Is performance degraded?
Should ipcs -m only show a maximum of six shared mem., segments afore
performance is impacted? ; Each pmon process takes at least one shared
memory segment.
e.g
# ipcs -m | grep oracle
m 131080 0x1883dd84 --rw-r----- oracle dba
m 32777 0xf36e5128 --rw-r----- oracle dba
m 65546 0x58d5f298 --rw-r----- oracle dba
m 32779 0xeb079cb4 --rw-r----- oracle dba
m 65548 0xcc76dbcc --rw-r----- oracle dba
m 32781 0xaf9e2c2c --rw-r----- oracle dba
# ps -eaf|grep pmon
oracle 18861 1 0 11:54:44 ? 0:00 ora_pmon_1PRD
oracle 17349 1 0 11:51:12 ? 0:01 ora_pmon_2PRD
oracle 17170 1 0 11:50:59 ? 0:00 ora_pmon_3PRD
oracle 21703 1 0 12:11:45 ? 0:00 ora_pmon_4PRD
oracle 17325 1 0 11:51:09 ? 0:00 ora_pmon_5PRD
root 3310 3117 0 13:07:50 pts/1 0:00 grep pmon
oracle 16960 1 0 11:50:21 ? 0:00 ora_pmon_6PRD
Any clues would be gratefully appreciated.
Merry Xmas & a happy New Year!
Regards, S.
------------------------------------------------------------------------------------------------
http://download.oracle.com/docs/html/A97297_01/appb_hp.htm
HP-UX Shared Memory Segments for a 64-Bit Oracle Instance
When a 64-bit Oracle server creates a database instance, the server
creates memory segments by dividing the available shared memory by the
value of the HP-UX SHMMAX kernel parameter. For example, if 64 GB of
shared memory is available for a single Oracle instance and the value of
the SHMMAX parameter is 1 GB, the Oracle server creates 64 shared memory
segments for that instance.
In laboratory tests, performance degradation occurs when an Oracle
instance creates more than six shared memory segments. This is because
each shared memory segment receives a unique protection key when the
Oracle server creates the instance. There are six protection keys
available for shared memory segments on the PA-RISC processor. If your
system has more than six shared memory segments, the HP-UX operating
system displays protection key faults.Oracle Corporation recommends that
you set the SHMMAX parameter value to the amount of available physical
memory on the system. Doing this ensures that the entire shared memory for
a single Oracle instance is assigned to one shared memory segment and your
instance needs only one protection key. To display the list of active
shared memory segments on the system, enter the following command: $ ipcs
-m
--
Simon Loewenthal/Tele2
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******** IMPORTANT NOTICE ********
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Content-Type: text/html; charset="US-ASCII"
<br><font size=3 face="Arial">Dear all,<br>
<br>
I read the article below about setting the shared memory
for Oracle. My knowledge of Oracle is poorly. Does the article
imply that each instance of of the pmon process should only have six shared
memory segments afore it runs out of protection keys? </font>
<br>
<br><font size=3 face="Arial">What happens if there are two instances of
pmon running on the server each with six shared mem segments (12 in total)
- Is performance degraded?<br>
<br>
Should ipcs -m only show a maximum of six shared mem., segments afore
performance is impacted? ; Each pmon process takes at least one shared
memory segment. <br>
<br>
e.g <br>
<br>
# ipcs -m | grep oracle<br>
m 131080 0x1883dd84 --rw-r----- oracle
dba<br>
m 32777 0xf36e5128 --rw-r----- oracle
dba<br>
m 65546 0x58d5f298 --rw-r----- oracle
dba<br>
m 32779 0xeb079cb4 --rw-r----- oracle
dba<br>
m 65548 0xcc76dbcc --rw-r----- oracle
dba<br>
m 32781 0xaf9e2c2c --rw-r----- oracle
dba<br>
# ps -eaf|grep pmon <br>
oracle 18861 1 0 11:54:44 ?
0:00 ora_pmon_1PRD<br>
oracle 17349 1 0 11:51:12 ?
0:01 ora_pmon_2PRD<br>
oracle 17170 1 0 11:50:59 ?
0:00 ora_pmon_3PRD<br>
oracle 21703 1 0 12:11:45 ?
0:00 ora_pmon_4PRD<br>
oracle 17325 1 0 11:51:09 ?
0:00 ora_pmon_5PRD<br>
root 3310 3117 0 13:07:50 pts/1
0:00 grep pmon<br>
oracle 16960 1 0 11:50:21 ?
0:00 ora_pmon_6PRD<b><br>
</b></font>
<br><font size=3 face="Arial">Any clues would be gratefully appreciated.</font>
<br>
<br><font size=3 face="Arial">Merry Xmas & a happy New Year!</font>
<br>
<br><font size=3 face="Arial">Regards, S.</font>
<br>
<br><font size=3 face="Arial"><b>------------------------------------------------------------------------------------------------</b></font>
<br><font size=3 face="Arial"><b><br>
</b></font><font size=3 color=blue face="Arial"><b><u><br>
</u></b></font><a href=http://download.oracle.com/docs/html/A97297_01/appb_hp.htm><font \
size=3 color=blue face="Arial"><b><u>http://download.oracle.com/docs/html/A97297_01/appb_hp.htm</u></b></font></a><font \
size=3><br> </font><font size=4><b><br>
HP-UX Shared Memory Segments for a 64-Bit Oracle Instance </b></font><font \
size=3><br> <br>
When a 64-bit Oracle server creates a database instance, the server creates
memory segments by dividing the available shared memory by the value of
the HP-UX SHMMAX kernel parameter. For example, if 64 GB of shared memory
is available for a single Oracle instance and the value of the SHMMAX parameter
is 1 GB, the Oracle server creates 64 shared memory segments for that instance.
<br>
<br>
In laboratory tests, performance degradation occurs when an Oracle instance
creates more than six shared memory segments. This is because each shared
memory segment receives a unique protection key when the Oracle server
creates the instance. There are six protection keys available for shared
memory segments on the PA-RISC processor. If your system has more than
six shared memory segments, the HP-UX operating system displays protection
key faults.Oracle Corporation recommends that you set the SHMMAX parameter
value to the amount of available physical memory on the system. Doing this
ensures that the entire shared memory for a single Oracle instance is assigned
to one shared memory segment and your instance needs only one protection
key. To display the list of active shared memory segments on the system,
enter the following command: <i>$ ipcs -m</i><br>
</font>
<br>
<br><tt><font size=3>-- <br>
Simon Loewenthal/Tele2<br>
<br>
******** IMPORTANT NOTICE ********<br>
Please repect the X-Reply to klunky.co.uk. PGP available 0xD86A5A17. <br>
S/MIME PKCS12 key available for Lotus Notes: Please ask me for it.<br>
This e-mail (including any attachments) may contain information that is
confidential or otherwise protected from disclosure and it is intended
only for the addressees. If you are not the intended recipient, please
note that any copying, distribution or other use of information contained
in this e-mail (and its attachments) is not allowed. If you have received
this e-mail in error, kindly notify us immediately by telephone or e-mail
and delete the message (including any attachments) from your system.<br>
Please note that e-mail messages may contain computer viruses or other
defects, may not be accurately replicated on other systems, or may be subject
of unauthorized interception or other interference without the knowledge
of sender or recipient. Tele2 only send and receive e-mails on the basis
that Tele2 is not responsible for any such computer viruses, corruption
or other interference or any consequences thereof. It ought to be
obvious that my views do not represent my employer's views.<br>
</font></tt>
<br><font size=1 color=#808080 face="sans-serif"><br>
******** IMPORTANT NOTICE ********<br>
This e-mail (including any attachments) may contain information that is
confidential or otherwise protected from disclosure and it is intended
only for the addressees. If you are not the intended recipient, please
note that any copying, distribution or other use of information contained
in this e-mail (and its attachments) is not allowed. If you have received
this e-mail in error, kindly notify us immediately by telephone or e-mail
and delete the message (including any attachments) from your system.<br>
<br>
Please note that e-mail messages may contain computer viruses or other
defects, may not be accurately replicated on other systems, or may be subject
of unauthorized interception or other interference without the knowledge
of sender or recipient. Tele2 only send and receive e-mails on the basis
that Tele2 is not responsible for any such computer viruses, corruption
or other interference or any consequences thereof.</font>
<br>
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