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Re: 10g Memory Usage: 12 GB RAM & 5000 Connections ~ Need help understanding

From: <bdbafh_at_gmail.com>
Date: 28 Jun 2006 10:43:05 -0700
Message-ID: <1151516585.367596.109710@y41g2000cwy.googlegroups.com>

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.
>
> 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%.
>
> Any tutors out there who can enlighten me? :)
>
> Thanks!
> -Diana

Diana,

> I don't see a lot of swapping. Available memory doesn't get below 60
> MB, pagefile usage is around 30%.

60 MB free memory?
Its amazing that the OS did not grind to a halt.

I'd recommend to use no more than 75% of physical memory as an upper limit.
How about cutting back to an sga_max_size of 8 GB as a first pass?

-bdbafh Received on Wed Jun 28 2006 - 12:43:05 CDT

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