Re: 10g Memory Usage: 12 GB RAM & 5000 Connections ~ Need help understanding
- From: "hpuxrac" <johnbhurley@xxxxxxxxxxxxx>
- Date: 28 Jun 2006 10:29:50 -0700
DragonWoman wrote:
Hello everyone,
I'm looking for a little help explaining what's going on with my Oracle
memory usage. Here are the details:
MS Server 2003 R2 x64
Oracle 10g (64-bit)
12 GB physical RAM
SGA_MAX = 10G
SGA_TARGET = 8G
Auto Memory Management ON
Shared server connections
Here is what I am seeing. On startup, with no external connections
(using Perf Mon):
Private Bytes: 10.48 GB
Page File Bytes: 10.48 GB
Working Set: 0.22 GB
Virtual Bytes: 10.74 GB
So, I'm seeing all the SGA_MAX plus a few other things (PGA?) being
allocated and reserved (Private Bytes). Working set is small because
not much has happened yet.
I gradually ramped up to 5,000 connections over a couple of hours and
let it run for a while. Using Perf Mon, I monitored the CPU and memory
usage for 17 hours and see the following:
Private Bytes: 11.87 GB (Average) (Min: 11.11G, Max: 12.27G)
Page File Bytes: 11.87 GB (Average) (Min: 11.11G, Max: 12.27G)
Working Set: 0.92 GB (Average) (Min: 0.44G, Max: 1.18G)
Virtual Bytes: 12.24 GB (Average) (Min: 11.48G, Max: 12.68G)
The Auto Memory Tuning works like a charm, adjusting the large pool to
allow for the number of connections. Max UGA per connection works out
to 317 KB.
I guess I need someone to explain to me why the private bytes grows. I
mean, MAX_SGA is 10G, but when I check, the ASMM balances the SGA so
that even though the shared and large pools have grown, the buffer
cache has shrunk and it's still within 8 GB. So, that's 2 GB it's
reserved for SGA, but not using. Using shared server, PGA isn't that
big. So, why does the private bytes start at 10.5G and get up to
12.3G? I see the reading for "Page File" follows the Private Bytes
exactly.
I used Pslist (from sysinternals) just now and it lists VM and Private
VM as 4 GB for Oracle.exe.
If you take 8 gig for SGA and 4 gig for memory for oracle.exe doesn't
that get you up to your 12 gig?
Many people with servers that have this much RAM might consider
supporting 5000 connections with dedicated server.
I don't see a lot of swapping. Available memory doesn't get below 60
MB, pagefile usage is around 30%. Buffer cache hit ratio is 99.99%.
A lot of swapping?
Sorry we don't run windows here for oracle but wouldn't you want a
higher number for available memory on a machine that has this much
memory?
Current oracle performance tuning thinking discounts the useability of
cache hit ratios but one that is that high makes me wonder if you have
way too much memory devoted to it. If you cut your buffer cache down
by 50% do you still get 99.9 percent?
.
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