Hi Martha,
As a starting point I'd recommend taking a look at the hints & tips at
http://www-128.ibm.com/developerworks/linux/linux390/perf/tuning_rec_database_Oracle.html
The way that I'd personally tackle this problem is to get the DBA to run
STATSPACK to determine the smallest size that is acceptable for the Oracle
SGA, PGA etc. STATSPACK gives invaluable guidance for doing this. Once you
have an idea of the ideal SGA size then set your virtual machine memory to
be
db_block_buffers * db_block_size
----------------------------------------------------------- Bytes
(Obviously round up to a sensible boundary)
0.6
as per the hints and tips.
NOTE: this recommendation should only be used where db_block_buffers *
db_block_size is a sizeable number e.g. greater than a few hundred MB
for small values then base you sizing on LINUX recommendations and add
db_block_buffers * db_block_size BUT remember Oracle will not use the
buffer cache (see below).
Unless your databases are doing large amounts of (intentional) sequential
IO also make sure that db_file_multiblock_read_count is not large e.g. <=
8 with 0 being perfectly acceptable (again STATSPACK will help here). The
reason for this is large multiblock_reads require large amounts of SGA
which unless you are doing sequential IO simply wastes SGA.
Finally, follow the advice for your filesystem type at
http://www-128.ibm.com/developerworks/linux/linux390/perf/tuning_rec_database_Oracle_test.html
to set DISK_ASYNCH_IO etc.
What you are trying to achieve is allocate as much memory as required by
Oracle and then just enough for the rest of LINUX. Don't over allocate
memory to LINUX as it will simply use this for buffer cache which will not
help Oracle throughput..
Good luck
Andrew Gadsby
z Solution Specialist
IBM Systems and Technology Group
Martha McConaghy <[EMAIL PROTECTED]>
Sent by: Linux on 390 Port <[email protected]>
29/09/2008 22:33
Please respond to
Linux on 390 Port <[email protected]>
To
[email protected]
cc
Subject
Tuning Oracle memory use (fwd)
We have a bunch of Oracle databases running on SLES 10 in one of our z/9
partitions. We are only getting started with this, so we don't much (i.e.
nothing) about tuning Oracle to be a polite guest in this environment and
our DBA is just as new to it. He is getting advice from a vendor, but
I have no faith in that as they think a mainframe is just a big
PC....sigh...
Anyway, we are looking at memory usage on these servers and things don't
seem right to me. However, I know little to nothing about how Linux uses
memory. One servers hows physical memory at 99% used, but actual is
only at 9%. Swap is also at 99%. Those numbers don't sound healthy.
What types of things can our DBA do to tune how Oracle uses memory or
should I
just up its virtual storage and postpone the problem? (Our CP paging is
going
up dramatically too.)
Martha
----------------------------------------------------------------------
For LINUX-390 subscribe / signoff / archive access instructions,
send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or
visit
http://www.marist.edu/htbin/wlvindex?LINUX-390
Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
----------------------------------------------------------------------
For LINUX-390 subscribe / signoff / archive access instructions,
send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit
http://www.marist.edu/htbin/wlvindex?LINUX-390
