Oracle Memory Configuration on Windows Server

1
Oracle Memory Configuration on Windows Server

• Configuring Large Memory for Oracle on 32-bit and
  64-bit Windows

2
Objectives

• At the end of this module the student will
  understand the following concepts
• OS Memory Configuration
• 32-bit and 64-bit systems
• Boot.ini file
• /3GB, /PAE, and /NOPAE Switches
• Oracle Memory Configuration
• Awe enabled
• Performance Implications of 32-bit Oracle
• Advantages of 64-bit Oracle

3
32-bit Addressing

• 32-bit processors have address registers that are
  32-bits wide (can address up to 4GB physical RAM)
• Allows per process virtual address space of 4GB
  range (0 to 4,294,967,295 bytes)
• Each individual process gets its own virtual
  address space that can be up to 4GB
• This virtual address space is divided system
  and user space

4
User and System Virtual Address Space
5
4GT (4GB Tuning) with /3GB

• /3GB 4GB Tuning Feature reduces system space
  to 1GB, allowing 3GB for user space
• Add to boot.ini file and reboot to take effect
• For systems 4GB to 16GB only

6
32-bit Systems with PAE (36-bit)

• PAE- Physical Address Extension
• AKA Large Memory Support
• Allows 36-bit memory addressing
• Allows the IA32 processor to address up to 64GB
  of physical RAM
• Add /PAE switch in the boot.ini file and reboot
  server
• Adds translation layer to memory access

7
Windows 2003 /NOPAE Special Case (32-bit)

• New for Windows 2003 is the /NOPAE switch
• Forces Windows 2003 NOT to use PAE algorithms for
  memory access (there is overhead involved)
• Should be used on systems with 4GB or less and
  hot-add memory devices

8
Boot.ini Examples (32-bit)

• To use /3GB or /PAE, add the switches to the
  boot.ini file and reboot the server
• Note
• Using both /3GB and /PAE together conserves the
  most memory under 4 GB
• Using both /3GB and /PAE will limit memory
  addressability to 16 GB

9
32-bit Memory Size/Switch Chart
10
Support for /3GB and /PAE 32-bit

• Windows 2000 Advanced Server
• Windows 2000 Datacenter Server
• Windows 2003 Enterprise Edition
• Windows 2003 Datacenter Edition

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32-bit Max Memory Support on x86 based computers

• Windows 2003 Enterprise 32GB max
• Windows 2003 Datacenter 64GB max

12
AWE for 32-bit Oracle

• Address Windowing Extension
• AWE a set of APIs that allow programs to
  address memory locations outside of their 4GB
  virtual addressing range
• Available through 32-bit addressing
• With AWE programs reserve memory as non-paged
  (will not page out)

13
Implementing AWE with 32-bit Oracle

• Set the /PAE boot.ini flag
• Set the USE_INDIRECT_BUFFERSTRUE parameter in
  the Oracle initialization file.
• Use the DB_BLOCK_BUFFERS parameter in the
  initialization file instead of the DB_CACHE
  parameter.
• The AWE_WINDOW_SIZE registry parameter sets up a
  swap area in low memory to map data buffers in
  high memory
• Default size is 1 GB.

14
Performance Implications of 32-bit Memory
Management

• Memory split into two parts is not as efficient
  as memory in one segment
• Overhead is introduced
• 32-bit systems with 8 GB of RAM may not perform
  much better than systems with 4 GB of RAM.
• May need to add 12 GB of RAM to see a noticable
  return for the investment.

15
Performance Implications of 32-bit Memory
Management

• Memory above 4 GB can only be used for
  DATA_BUFFER cache.
• There is little room for the Shared Pool, Large
  Pool, PGA, etc.
• The AWE_WINDOW_SIZE parameter takes up 1 GB of
  RAM
• Leaves only 1 GB of RAM for all other memory
  types (2 GB with /3GB)
• The other memory types are required for
  supporting memory connections.
• As a result, Oracle on 32-bit systems is severely
  restricted on the number of user connections
  supported
• 100s low thousands with Shared Servers

16
Conserving Memory for User Connections

• AWE/PAE does not improve user connectivity for
  32-bit Oracle
• User connections must share a limited pool of
  memory, 1-2 GB
• The AWE_WINDOW_SIZE registry parameter can be
  decreased from 1 GB to as low as 512 MB to
  increase user memory
• Tradeoff between upper memory accessibility and
  user memory size

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Conserving Memory for User Connections

• Oracle initialization parameters can be used to
  decrease per user memory usage
• bitmap_merge_area_size
• create_bitmap_area_size
• hash_area_size
• open_cursors
• sort_area_size (sort_area_retained_size)
• The Orastack command can be used to decrease
  memory use per thread
• Default allocation is 1 MB
• Risky to decrease below 700KB any change must be
  tested
• Example usage
• orastack oracle.exe 700000
• orastack tnslsnr.exe 700000
• orastack svrmgrl.exe 700000
• orastack sqlplus.exe 700000

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Windows 2003 64-bit Systems

• 64-bit versions of Windows have implemented up to
  16 terabytes of virtual address space
• Dont use PAE or /3GB with 64-bit
• 64-bit programs use 16 terabyte tuning model (8TB
  user / 8TB kernel)
• Compare to 32-bit tuning mode (2GB user / 2GB
  kernel)
• No performance penalties for large memory
• Unlimited user connectivity

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64-bit Memory Support on Itanium based computers

• Windows 2003 Enterprise 64-bit 1TB max
• Windows 2003 Datacenter 64-bit 1TB max

20
64-bit Memory Support on EM64T and Opteron based
computers

• Windows 2003 Standard 64-bit 64GB
• Windows 2003 Enterprise 64-bit 1TB max
• Windows 2003 Datacenter 64-bit 1 TB max

21
Monitor Oracle Memory

• Oracle for Windows Performance Counters
• Oracle phyreads/gets shows Buffer Cache
  performance
• Should be below 10 - few physical reads as a
  proportion of all reads otherwise, more memory
  may be required

22
Review

• What flag is set in the boot.ini file to use
  memory above 16 GB?
• Which two flags may be set in the boot.ini file
  for memory between 4 GB and 16 GB?
• What are the performance implications of 32-bit
  memory management for Oracle?
• What tool may be used to monitor Buffer Cache
  efficiency?

23
Summary

• The following topics were discussed in this
  training module
• OS Memory Configuration
• 32-bit and 64-bit systems
• Boot.ini file
• /3GB, /PAE, and /NOPAE Switches
• Oracle Memory Configuration with AWE
• Performance Implications of 32-bit Oracle
• Advantages of 64-bit Oracle