windows 2003 x32中 设置oracle SGA内存使用大于1.7的方法--PAE

         转自[url]http://space.itpub.net/10834762/viewspace-445622[/url]

设置32位的 windows 2003 使用大于1.7的内存

前两天出差遇到:32位的windows 2003 使用大于1.7的内存的问题，PC server上内存为16G, 但由于32位的CPU的在windows系统中2G给系统用2G给应用程序使用，如系统及 oracle参数不作修改时，oracle的 SGA内存使用不能超过1.7G，所以要对一些进行windos
ows和oracle参数据进行修改,大致有以下几步：

一 windows 上的参数据修改：
   1. 修改boot.ini文件，加/3GB /PAE:
      在这行，multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows" /3GB /PAE

   2.修改windows 注册表:
     regedit到HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\HOME0 这个目录中找到AWE_WINDOW_MEMORY这个参数，将其修改为oracle需要内存的大小:例如：6G时为：6*1024*1024*1024
     这个参数如不存大时，可以新建一个字符串名为AWE_WINDOW_MEMORY，值为上面讲过的大小,这个值需要足够大，不够时将报：
         ORA-27102 out of memory
         OSD-00034 Message 34 not found;  Product=RDBMS;facility =SOSD
         O/S Error: (OS 8) Not enough storage is available to process this command

   3.修改windows控制面板中的 管理工具-->  域安全策略--> 本地安全策略 -->锁定内存页 中加入启oracle数据库的OS用户名.

二 ORACLE数据库中要改的参数：
   1.在改参数之前最好能先 备份一个spfile到pfile 文件以防 数据库修改失败时可以从这个参数文件在启动数据库: create pfile='d:\inittest.ora' from spfile;

   2.主要修改的参数为：
     _db_block_lru_latches --这个参数据大小为=CPU数*2*8
     取消参数据：db_cache_size,sga_max_size  
     db_block_buffers
     USE_INDIRECT_DATA_BUFFERS=TRUE 
 

SQL> shutdown immediate;
数据库已经关闭。
已经卸载数据库。
ORACLE 例程已经关闭。
SQL> startup
ORACLE 例程已经启动。

Total System Global Area 1008280152 bytes
Fixed Size                   455256 bytes
Variable Size             478150656 bytes
Database Buffers          528482304 bytes
Redo Buffers                1191936 bytes
数据库装载完毕。
数据库已经打开。
SQL> alter system set "_db_block_lru_latches"=128 scope=spfile;

系统已更改。

SQL> alter system reset db_cache_size scope=spfile sid='*';

系统已更改。

SQL> alter system set lock_sga=false scope=spfile;

系统已更改。

SQL> alter system set db_block_buffers=1179648 scope=spfile;

系统已更改。

SQL> alter system set use_indirect_data_buffers=true scope=spfile;

系统已更改。

SQL> create pfile='d:\init2.ora' from spfile;

文件已创建。

SQL> shutdown immediate;
数据库已经关闭。
已经卸载数据库。
ORACLE 例程已经关闭。

可以通过OEM来修改PGA,shared pool这些内存大小

SQL> startup
ORACLE 例程已经启动。

Total System Global Area 7516192768 bytes
Fixed Size                   455256 bytes
Variable Size             478150656 bytes
Database Buffers          3528482304 bytes
Redo Buffers                1191936 bytes
数据库装载完毕。
数据库已经打开。

 

下为metalink为文章：

Subject:	Implementing Address Windowing Extensions (AWE) or VLM on Windows Platforms
	Doc ID:	Note:225349.1	Type:	BULLETIN
	Last Revision Date:	11-JUL-2007	Status:	PUBLISHED

PURPOSE
-------

To address the growing need for use of more memory on 32-Bit Windows platforms,
and explain how AWE is implemented by Oracle on Windows.

 
SCOPE & APPLICATION
-------------------
    Oracle DBA's running on the Microsoft Windows platform.
    Oracle Support Analysts, Field Engineers troubleshooting problems
    related to AWE and/or memory issues on Windows.

AWE Memory implementation on Windows 2000
------------------------------------------
 
    A common question on the Windows NT/Windows 2000 platform. revolves around 
    how to take advantage of systems with more than 4 GB of RAM.  As discussed 
    in MetalinkNote 46001.1andNote 46053.1, the 32-Bit process address 
    space for any process on Windows equates to a total of 4GB of addressable 
    RAM. Of this, by default, 2GB is reserved for the process itself, and 2GB 
    for the kernel.  On systems running either Windows 2000 Advanced Server, 
    or Windows NT 4.0 Enterprise Edition, this ratio can be changed by adding 
    the /3GB switch to the boot.ini, allowing a process to address 3GB and 
    reserving 1GB for the kernel.  However, the total addressable memory for
    a single process is still only 4GB.
    See alsoNote 1036312.6: Utilizing Up to 3GB Virtual Memory on Windows NT Server 4.0


__________________________________________________________________

What can be done to address memory beyond 4GB?:
===============================================


    The answer is to take advantage of Physical Address Extensions (PAE), or 
    Address Windowing Extensions (AWE)(These two terms are used interchangeably, 
    so the rest of this document will refer to this simply as AWE). 
    AWE support is available if you are running on a machine with more than 4GB   
    of physical RAM which is running any of the below Windows operating systems:

    * Windows 2000 Datacenter Server
    * Windows 2000 Advanced Server
    * Windows 2003 Data Center Edition (32-Bit)
    * Windows 2003 Enterprise Edition (32-Bit) 

    On the above operating systems, AWE support is built into the OS.  No
    special drivers are needed to take advantage of the additional memory.

  AWE CANNOT be used on the following Operating Systems:

    * Windows 2000 Server (Standard)
    * Windows 2000 Professional
    * Windows XP Home Edition
    * Windows XP Professional
    * Windows 2003 Standard Edition
    * Windows 2003 Web Edition

   NOTE Also that on 64-Bit Windows operating systems, there is no need for AWE
   implementation support, because the directly addressable memory for a single
   process on 64-Bit Windows is 8 Terabytes.

__________________________________________________________________

Oracle versions that can use AWE:
=================================

    Oracle can take advantage of AWE in the following 32-Bit RDBMS releases:

    * Oracle 8.1.6.x
    * Oracle 8.1.7.x
    * Oracle 9.2.x
    * Oracle 10.1.x
    * Oracle 10.2.x

   Oracle does NOT implement AWE support in release 9.0.1.x


   AWE support is available on both the Enterprise Edition of Oracle and
   the Standard Edition of Oracle.  However, on Standard Edition of 9.2.0.1, 
   you may receive the following error if trying to start the database with
   USE_INDIRECT_DATA_BUFFERS=TRUE:

   ORA-439 - FEATURE NOT ENABLED: VERY LARGE MEMORY

   In Standard Edition 9.2.0.2 and 9.2.0.3, you will not receive the above errors, 
   but VLM functionality is still not enabled.  Refer to BUG#2945011 for more detail.
   This BUG is fixed in 9.2.0.3 Patch 2, and will be fixed in 9.2.0.4 as well.

__________________________________________________________________

Enabling support at the OS level:
==================================

    AWE can be enabled at the OS by adding the /PAE switch to the boot.ini 
    as such:

multi(0)disk(0)rdisk(0)partition(1)\WINNT="Microsoft Windows 2000 Advanced Server" /PAE

    It IS possible to have BOTH the /PAE and /3GB switch in place on the same
    machine, as such:

multi(0)disk(0)rdisk(0)partition(1)\WINNT="Microsoft Windows 2000 Advanced Server" /3GB /PAE

    However, be aware that if BOTH switches are in place, the server will only
    be able to recognize up to 16GB of RAM.  If you are working with a server 
    with more than 16GB of RAM, you will need to choose between the two.

    It is important to note that once either or both of these switches are in
    place in the boot.ini, ALL processes running can take advantage of these
    switches.  Thus, in a case where multiple Oracle instances are running on
    the same server, ALL instances can take advantage of the additional memory                
    afforded by these switches, up to the amount of physical memory on the box.


Operating System Privileges Needed at the OS Level:
====================================================

   In order to take advantage of the additional memory afforded through PAE,
   the operating system user account which is used to start the OracleService<SID>
   must be granted the 'Lock Pages in Memory' system privilege at the operating system
   level.   By default, the OracleService<SID> starts as the LocalSystem account.
   The LocalSystem account has the privilege to Lock Pages in Memory granted to 
   it by default.

   However, if you change the OracleService<SID> to logon as a user OTHER than
   LocalSystem, you may see the following errors when attempting to start the
   database with USE_INDIRECT_DATA_BUFFERS set to TRUE :


   SQL> startup pfile=c:\temp\initscott.ora
   ORA-27102: out of memory
   OSD-00010: Message 10 not found;  product=RDBMS; facility=SOSD
   
   O/S-Error: (OS 1300) Not all privileges referenced are assigned to the caller.


   To rectify this, you must grant the 'Lock pages in memory' privilege to the user
   that the OracleService<SID> starts as.  To do this, click on:
   Start ->  Programs -> Administrative Tools -> Local Security Policy
   (on a Domain Controller, click on 'Domain Security Policy' instead of 'Local Security Policy')
   Double-click on the 'Lock Pages in memory' policy.
   Add the appropriate user and click 'Ok'.
   Restart the OracleService<SID>


__________________________________________________________________

Understanding the Oracle implementation of AWE support:
=======================================================

    What the PAE switch allows you to do from the Oracle perspective is to 
    increase the amount of memory that can be used for the Oracle Database 
    Block Buffer Cache.  It is important to note that this additional memory 
    can ONLY be used by Oracle in the form. of an increased value for 
    DB_BLOCK_BUFFERS.  

    There is still confusion on the old style. of VLM versus AWE on Windows 2000. 
    With VLM on Windows NT 4.0, there was the concept of pointers pointing to 
    the extended memory area, but that is no longer the case on Windows 2000.
    Instead, the windowing technology as described in these articles is being 
    used.  For more information on AWE/PAE implementation on the Windows 
    platform, refer to Microsoft's website.

    As mentioned previously, with AWE enabled, this allows the process(es) 
    (in this case ORACLE.EXE) to use memory above and beyond the 4GB 
    mark defined by a 32-Bit Process Address space.  The physical location of 
    these blocks does not matter.  However, the database blocks must still be 
    accessed from within a ‘window’, which exists (logically) in that regular 
    3GB process address space. 
    The size of this window is defined by a registry setting in the HOME key for 
    Oracle (HKLM\Software\Oracle\Homex) called AWE_WINDOW_MEMORY.  By default, 
    this value is 1GB, so if this value is not set in the registry,  
    AWE_WINDOW_MEMORY will be 1GB.  

    If you add the registry key yourself, the datatype should be a string value, 
    or a REG_SZ.   The value for AWE_WINDOW_MEMORY must be specified in BYTES.

    It is important to realize that any database blocks accessed by Oracle 
    (or any user/background thread within Oracle.exe) must first be mapped into 
    the 'window' defined by AWE_WINDOW_MEMORY.  In this scenario, it does not
    matter where the blocks are physically located - there is no need to be 
    concerned with where the blocks are physically residing.  The window will be 
    drawn around the block (i.e. the block will be mapped) wherever it is located  
    in memory.  If the block is in memory but has not been mapped into the 
    ‘window’, then it may be necessary to unmapped another block that IS in the 
    window, in order to accommodate the new block.  While this mapping and 
    unmapping of blocks does add some cost, it is still faster than incurring 
    an I/O operation to read the block from disk.  This will be discussed 
    further down in the section on troubleshooting.
    
    Note:   

    Keep in mind that if there are multiple instances on a machine with 
    the /PAE switch enabled, ALL instances can take advantage of the additional 
    memory.  However, AWE_WINDOW_MEMORY cannot be set on a per-instance basis,
    so all databases that are running out of the HOMEx key where 
    AWE_WINDOW_MEMORY is set will inherit the same value.


__________________________________________________________________

Enabling AWE Support at the Database/Instance Level:
====================================================

    To enable the AWE implementation on Oracle, you must set the following 
    parameter in the init file (or spfile) used to start the instance:

      USE_INDIRECT_DATA_BUFFERS=TRUE

    Note again that the buffer cache MUST be defined using the parameter 
    DB_BLOCK_BUFFERS, no matter what version of the RDBMS you are running.  
    The 9.2 feature allowing for Multiple block sizes in a database will be 
    disabled if you set USE_INDIRECT_DATA_BUFFERS=TRUE, and you cannot specify 
    the DB_CACHE_SIZE parameter to define the size of the buffer cache.
    

    On 9.2, if you attempt to startup a database with this combination of 
    parameters:

      USE_INDIRECT_DATA_BUFFERS=TRUE
      DB_CACHE_SIZE=xxxxx (Any number)

    The startup will fail with the following error:


      SQL> startup
      ORA-00385: cannot enable Very Large Memory with new buffer cache 
      parameters

    You must change DB_CACHE_SIZE to use DB_BLOCK_BUFFERS instead, as was the 
    syntax under Oracle8i and earlier.



__________________________________________________________________

AWE_WINDOW_MEMORY Within the 3GB Process Address Space:
=======================================================

    If you are using /PAE and the /3GB switch together, the address space for 
    ORACLE.EXE will be 3GB.  The value for AWE_WINDOW_MEMORY must come from the 
    normal address space used by the ORACLE.EXE process.  Memory that comes 
    from that 3GB address space addressable by the oracle.exe process includes
    the following:


     ・The Value for AWE_WINDOW_MEMORY
     ・The rest of the SGA (shared_pool, large_pool, java_pool, log_buffers, etc)
     ・Overhead for Oracle.exe and DLL’s (65-100M depends on version & options)
     ・Stack space for all threads (Defaults to 1MB/thread, unless orastack 
         is used)
     ・PGA and UGA memory for all user sessions

    Therefore, the value for AWE_WINDOW_MEMORY should be tuned such that mapping
    and unmapping operations are avoided as much as possible, while still 
    allowing enough memory within the 3GB address space for the rest of the 
    process memory that MUST fit within the 3GB (i.e. overhead, remaining SGA
    components and all user connection memory (stack + uga + pga) noted above).

    The total size of the buffer cache can then be set to the amount of 
    physical memory remaining above the 4GB barrier, plus AWE_WINDOW_MEMORY.
    On a machine with 12GB of RAM, using the default value of 1GB for 
    AWE_WINDOW_MEMORY, your total buffer cache could theoretically be as high 
    as 9GB:

     (Total RAM - 4GB + AWE_WINDOW_MEMORY) = 12GB - 4GB + 1GB = 9GB

    In reality, your maximum buffer cache size will be somewhat less than 
    this, allowing for some overhead and additional processes running on the 
    system. 

    Attempting to startup the database with a buffer cache larger than the 
    maximum value as calculated above may result in the following errors:

      ORA-27102 out of memory 
      OSD-00034 Message 34 not found;  Product=RDBMS;facility =SOSD 
      O/S Error: (OS 8) Not enough storage is available to process this command

    (Note - If you are on Release 9.2, another possible cause for these errors 
    is  noted further down, in the troubleshooting section)

    As mentioned above, the buffer cache must be specified using 
    DB_BLOCK_BUFFERS rather than DB_CACHE_SIZE, so assuming an 8K block 
    size (8192), to get a 9GB buffer cache, you would set the following init 
    parameters:

      DB_BLOCK_BUFFERS = 1179648
      DB_BLOCK_SIZE = 8192


__________________________________________________________________

Troubleshooting AWE_WINDOW_MEMORY implementation:

=========================
=========================

Minimum Value Required for AWE_WINDOW_MEMORY in 9.2 and Above:
==============================================================

    Here are key points to understand when using AWE_WINDOW_MEMORY:

     1.  Under Oracle 8.1.7 we do NOT enforce a minimum value for 
         AWE_WINDOW_MEMORY to be able to start the database.
     2.  This was changed under Oracle9i Release 2, such that we DO 
         enforce a minimum value for AWE_WINDOW_MEMORY. This change was 
         done to help improve performance by enforcing a larger window size.
     3.  You can alter the minimum required value for AWE_WINDOW_MEMORY 
         under 9.2 by changing/setting the value of the parameter 
         _DB_BLOCK_LRU_LATCHES.  Under 8.1.7, this parameter was named 
         DB_BLOCK_LRU_LATCHES.  However, under 9.x, this parameter was 
         changed to be a hidden parameter.

    The minimum value for AWE_WINDOW_MEMORY starting with 9.2 is calculated as such:

    MIN(AWE_WINDOW_MEMORY)=(4096 * DB_BLOCK_SIZE * _DB_BLOCK_LRU_LATCHES)/8

    Starting with 9.2, to calculate the value for _DB_BLOCK_LRU_LATCHES, we need 
    this formula:

    _DB_BLOCK_LRU_LATCHES = (Max buffer pools * SETS_PER_POOL) 

    Max Buffer Pools is a constant = 8
    SETS_PER_POOL is variable, and depends on whether or not VLM is enabled.

    SETS_PER_POOL = 2* CPU_COUNT   (if VLM is enabled)
    SETS_PER_POOL= CPU Count /2  (If VLM is NOT enabled)

    /* Recall that VLM is enabled by setting USE_INDIRECT_DATA_BUFFERS=TRUE

    So, as you can see, the value for _DB_BLOCK_LRU_LATCHES in 9.2 and above is 
    dependent on the number of CPU's in the box, and therefore 
    MIN(AWE_WINDOW_MEMORY) is dependent on the # of CPU's as well as the 
    DB_BLOCK_SIZE.  The larger the Block Size, and the more CPU's in a system,
    the higher the value for MIN(AWE_WINDOW_MEMORY). Here are a couple of 
    example configurations and caclulations showing MIN(AWE_WINDOW_MEMORY).


    Example #1:
    ----------------
      # of CPU's = 8
      DB_BLOCK_SIZE = 8192
      Total RAM = 8GB

      SETS_PER_POOL = 2 * CPU_COUNT = 16
      _DB_BLOCK_LRU_LATCHES = (max buffer Pools * sets_per_pool) = 8*16 = 128
      MIN(AWE_WINDOW_MEMORY) =(4096*DB_BLOCK_SIZE*_DB_BLOCK_LRU_LATCHES)/8 = 
      ( 4096 * 8192 * 128) / 8 = 536870912 bytes = 512 MB


    Example #2:
    ---------------
      # of CPU's = 16
      DB_BLOCK_SIZE = 8192
      Total RAM = 16 GB

      SETS_PER_POOL = 2 * CPU_COUNT = 32
      _DB_BLOCK_LRU_LATCHES = (max buffer Pools * sets_per_pool) = 8*32 = 256
      MIN(AWE_WINDOW_MEMORY) =(4096*DB_BLOCK_SIZE*_DB_BLOCK_LRU_LATCHES)/8 = 
      ( 4096 * 8192 * 256) / 8 = 1073741824 bytes = 1024 MB


    
    These values above are the minimum values required for AWE_WINDOW_MEMORY 
    to be set to, UNLESS you explicitly set _DB_BLOCK_LRU_LATCHES to a lower
    value.  If AWE_WINDOW_MEMORY is not set to the minimum value, you will 
    receive the following errors:

      ORA-27102 out of memory 
      OSD-00034 Message 34 not found;  Product=RDBMS;facility =SOSD 
      O/S Error: (OS 8) Not enough storage is available to process this command

    If you receive these errors when trying to start the database under 9.2 or 10g, 
    this may be because the AWE_WINDOW_MEMORY value in the registry is set 
    too low for the calculated minimum value.  If you cannot increase the 
    value for AWE_WINDOW_MEMORY, then you can explicitly set 
    _DB_BLOCK_LRU_LATCHES to a value lower than the calculated value, and 
    retry the startup.

    _DB_BLOCK_LRU_LATCHES must be at least 8 (Equal to the maximum number of
    buffer pools)

    Note #1 - Recall from the earlier section that these errors may also occur if
    you are trying to start up with a buffer cache that is too large for the 
    physical memory available.

    Note #2 - The same errors above have also been observed with a buffer
    cache that is too small.  When USE_INDIRECT_DATA_BUFFERS is set to TRUE
    the value for DB_BLOCK_BUFFERS should equate to a buffer cache that is
    AT LEAST equal to AWE_WINDOW_MEMORY.  In most cases, the total buffer
    cache size will be greater than AWE_WINDOW_MEMORY.  If you attempt to 
    start up with a buffer cache that is too small (i.e. < AWE_WINDOW_MEMORY)
    that may also result in the ORA-27102 error.

    Note#3 - It has been observed on some systems that you may need to add a few
    additional meg to AWE_WINDOW_MEMORY to calculate for overhead.  Therefore, if
    you go through the above calculations, and the instance still does not start,
    try adding an additional 10 Meg or so to the calculated value.
 
    Note#4 - Also, keep in mind that when calculating the # of CPU's in the system,
    you have to take hyperthreading into account.  On a hyperthreaded system, the OS
    will think that you have double the # of CPU's in the system over what you actually 
    have, and this is the number that must be used in the calculations.


How to calculate the maximum used memory
=========================================
    With respect to awe_window_memory the following maximum amount of memory can be used
    from physical memory: 

    The SGA size is composed from:
    ((db_block_buffers * block size) +  (shared_pool_size + large_pool_size + 
    java_pool_size + log_buffers) + 1MB
    The size of SGA + Oracle's overhead  must not exceed the available virtual memory.

    The size of buffer cache depends on the available virual memory and can be calculated with
    buffer cache = db_block_buffer * db_block_size


CPU Spins Possible When Using AWE Implementation:
=================================================

    Use caution when setting _DB_BLOCK_LRU_LATCHES or AWE_WINDOW_MEMORY too low. 
    If we are unable to map a requested buffer into the window because all of 
    the space  defined by AWE_WINDOW_MEMORY is in use with buffers already 
    actively being accessed, then we spin and wait, checking every so often 
    until an existing buffer in the window can be unmapped, and a new buffer can
    be mapped in. 
 
    This spin will consume CPU cycles until enough buffers can be 
    Mapped/Unmapped to satisfy the request.  In some cases, there may be so 
    many buffers needing to be mapped into the window, that DBWR will consume 
    100% of cycles on all CPUs, effectively locking up the machine.  This is 
    normal behavior. under some circumstances, and is simply an indication that 
    AWE_WINDOW_MEMORY is too small.  

Monitoring Mapping Operations in 9.2 and later releases:
========================================================

    Starting with 9.2, we have added additional statistics which can be 
    measured in v$sesstat (sesssion-level stats) and v$sysstat (system-wide 
    stats):

    STATISTIC# NAME
    ---------- ------------------------------
    154 number of map operations
    155 number of map misses

    This query below will give you system-wide information on map 
    operations and map misses:
    
      SQL> select * from v$sysstat where statistic# in (154, 155);

    If the # of Map misses is relatively high, or particularly of the # of map
    misses increases consistently over time, this may be an indication that the
    value for AWE_WINDOW_MEMORY is set too low.

    
    Note that the statistic#'s change from version to version, so the below query
    will allow you to determine the statistic# for your particular DB version.
    this example is from a 10gR2 database:

SQL> select statistic#, name from v$sysstat where name like '%map %';

STATISTIC# NAME
---------- ----------------------------------------------------------------
       168 number of map operations
       169 number of map misses


   So simply substitute in the correct statistic#, depending on your DB version.

Dynamic Memory Management/Automatic Memory Management with AWE Enabled
=============================================================

Oracle10g introduces the concept of Automatic Memory Management, 
whereby the Oracle RDBMS will dynamically adjust SGA parameters 
such as SHARED_POOL_SIZE, JAVA_POOL_SIZE, DB_CACHE_SIZE, etc.

This is enabled by setting the parameter SGA_TARGET to a non-zero value.
However, in order for this to work properly, you must use DB_CACHE_SIZE
for the buffer cache.   When setting USE_INDIRECT_DATA_BUFFERS, you cannot
set DB_CACHE_SIZE, as noted above.  Therefore, SGA_TARGET should not be set
when using AWE - these two features are mutally exclusive.
When setting USE_INDIRECT_DATA_BUFFERS=TRUE on Oracle10g, you should also
set SGA_TARGET to 0.


Diagnosing Spins Associated With AWE in 8.1.x:
==============================================

    The above stats are not available in 8.1.7, so if you are encountering 
    problems with CPU spins, with AWE_WINDOW_MEMORY enabled, it is more 
    difficult to diagnose.

    You can start by identifying and monitoring the thread associated with 
    DBWR via the following query:

      SQL> select b.name, p.spid  from v$process p, v$bgprocess b
      where p.addr=b.paddr;

      NAME  SPID
      ----- ---------
      PMON  1900
      DBW0  1956
      LGWR  572
      CKPT  1908
      SMON  1808
      RECO  920
      SNP0  1784
      SNP1  1892
      SNP2  1896
      SNP3  1844

      10 rows selected.

    As you can see, DBWR has an SPID of 1956, which will equate to the 
    Thread ID of that thread within the Oracle executable.  This thread can 
    then be monitored using Performance Monitor and/or the PSLIST utility, 
    which is available as a free download from [url]http://www.sysinternals.com[/url]

    If your monitoring shows that DBWR is consuming excessive CPU, you can 
    attempt to get an errorstack from that thread using oradebug:

      SQL> oradebug setospid 1956
      Oracle pid: 3, Windows thread id: 1956, image: ORACLE.EXE
      SQL> oradebug unlimit
      Statement processed.
      SQL> oradebug dump errorstack 3
      Statement processed.

    This should dump the errorstack to the DBWR trace file, found in BDUMP.  
    If the errorstack contains the function SKGMMAP, this is an indication 
    that DBWR is working to map/unmap database block buffers.

Note:   In 8.1.7 of the RDBMS, you cannot use DBWR_IO_SLAVES in combination with
USE_INDIRECT_DATA_BUFFERS, due to BUG#3042660/BUG#2215894.  You must leave
DBWR_IO_SLAVES at its default value - otherwise, buffers are not unmapped
and eventually a spin of the process will result.
This problem is resolved in 9.2.0.1 - the fix is NOT backported to 8.1.7

KNOWN ISSUES
--------------------
BUG#2461474 - SHOW SGA DOES NOT SHOW CORRECT # OF DB BUFFERS412485 - LONG SHUTDOWN TIME WITH AWE_WINDOW_MEMORY: FIXED IN 8.1.7.1
BUG#1406194 - AWE_WINDOW_MEMORY NOT RELEASED WHEN DB SHUTDOWN:  FIXED IN 8.1.7.1
BUG#2520796 - ORA-439 TRYING TO ENABLE VLM IN STANDARD EDITION OF ORACLE - FIXED IN 9.2.0.4
BUG#2945011 - VLM DOES NOT WORK ON STANDARD EDITION ORACLE 9.2.0.2 ON WINDOWS - FIXED IN 9.2.0.4
BUG#3120033 - ORA-600[KCBVMAP] may occur with AWE, or DBWR may crash with ORA-471 on 9.2.0.4 - FIXED 9.2.0.4 PATCH 2
BUG#3042660 / BUG#2215894 - IO SLAVES DON'T UNMAP BUFFERS ON LINUX IN VLM MODE (APPLIES TO WINDOWS AS WELL)

RELATED DOCUMENTS
-----------------Bug 1803377- WINDOWS AWE MEMORY AND CPU - CAN'T MAP THE BUFFERNote 46001.1- Oracle Database and the Windows NT memory architectureNote 46053.1- Windows NT Memory Architecture Overview

Oracle 8.1.7 Release Notes for Windows:
[url]http://download-west.oracle.com/docs/pdf/A85305_01.pdf[/url]

Oracle9i Database Getting Started
Release 2 (9.2) for Windows
Part Number A95490-01
Chapter 4: Oracle9i Architecture on Windows
[url]http://download-west.oracle.com/docs/cd/B10501_01/win.920/a95490/architec.htm#1005809[/url]

Oracle® Database Platform. Guide
10g Release 1 (10.1) for Windows
Part Number B10113-01
Chapter 1:  Oracle Database Architecture on Windows
[url]http://otn.oracle.com/pls/db10g/portal.portal_[/url]
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