What is maximum amount of memory that oracle db can utilize ?

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What is maximum number of memory that oracle database can utilize for each of its memory structure like sga, caches....
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Answer 1

ps, the following may help too
VLM) Configurations
Oracle Database for Windows supports Very Large Memory (VLM) configurations in Windows 2000, Windows 2003, and Windows XP, which allows Oracle Database to access more than the 4 gigabyte (GB) of RAM traditionally available to Windows applications.
Note:
This feature is available on Windows 2000, Windows 2003, and Windows XP only with Intel Pentium II and above processors.
Specifically, Oracle Database uses Address Windowing Extensions (AWE) built into Windows 2000, Windows 2003, and Windows XP to access more than 4 GB of RAM.
The requirements for taking advantage of this support are:
1. The computer on which Oracle Database is installed must have more than 4 GB of memory.
2. The operating system must be configured to take advantage of Physical Address Extensions (PAE) by adding the /PAE switch in boot.ini. See Microsoft Knowledge Base article Q268363 for instructions on modifying boot.ini to enable PAE.
3. It is advisable (though not necessary) to enable 4GT support by adding the /3GB parameter in boot.ini. See Microsoft Knowledge Base article Q171793 for additional requirements and instructions on modifying boot.ini to enable 4GT.
4. The user account under which Oracle Database runs (typically the LocalSystem account), must have the "Lock memory pages" Windows 2000 and Windows XP privilege.
5. USE_INDIRECT_DATA_BUFFERS=TRUE must be present in the initialization parameter file for the database instance that will use VLM support. If this parameter is not set, then Oracle Database 10g Release 1 (10.1) or later behaves in exactly the same way as previous releases.
6. Initialization parameters DB_BLOCK_BUFFERS and DB_BLOCK_SIZE must be set to values you have chosen for Oracle Database.
Note:
The total number of bytes of database buffers (that is, DB_BLOCK_BUFFERS multiplied by DB_BLOCK_SIZE) is no longer limited to 3 GB.
Dynamic SGA and multiple block size are not supported with VLM. When VLM is enabled, the following new buffer cache parameters are not supported:
o DB_CACHE_SIZE
o DB_2K_CACHE_SIZE
o DB_4K_CACHE_SIZE
o DB_8K_CACHE_SIZE
o DB_16K_CACHE_SIZE
o DB_32K_CACHE_SIZE
To select the block size for the instance, use the initialization parameter DB_BLOCK_SIZE. The buffer cache size is set by the initialization parameter DB_BLOCK_BUFFERS.
7. Registry parameter AWE_WINDOW_MEMORY must be created and set in the appropriate key for your Oracle home. This parameter is specified in bytes and has a default value of 1 GB. AWE_WINDOW_MEMORY tells Oracle Database how much of its 3 GB address space to reserve for mapping in database buffers.
This memory comes from the 3 GB virtual address space in Oracle Database, so its value must be less than 3 GB. Setting this parameter to a large value has the effect of using more of the address space for buffers and using less AWE memory for buffers. However, since accessing AWE buffers is somewhat slower than accessing virtual address space buffers, Oracle recommends that you tune these parameters to be as large as possible without adversely limiting database operations.
In general, the higher AWE_WINDOW_MEMORY is set, the fewer connections and memory allocations will be possible for Oracle Database. The lower AWE_WINDOW_MEMORY is set, the lower the performance.
8. Once this parameter is set, Oracle Database can be started and will function exactly the same as before except that more database buffers are available to the instance. In addition, disk I/O may be reduced because more Oracle Database data blocks can be cached in the System Global Area (SGA).
Note:
Registry parameter VLM_BUFFER_MEMORY, which enabled VLM configurations in earlier releases, is not supported in Oracle Database 10g Release 1 (10.1) or later.
VLM Instance Tuning
VLM configurations improve database performance by caching more database buffers in memory. This reduces disk I/O compared to configurations without VLM. VLM support in Oracle Database 10g Release 1 (10.1) or later has been re-written to integrate very closely with Windows. Compared to Oracle8i release 2 (8.1.6), VLM users should see better performance with the newer implementation.
Tuning for VLM is no different than tuning for configurations without VLM. It is an iterative task that begins by selecting appropriate DB_BLOCK_SIZE and DB_BLOCK_BUFFERS initialization parameters for the application being supported.
Note:
Oracle Database 10g Release 1 (10.1) or later VLM configurations do not support multiple database block sizes.
AWE_WINDOW_MEMORY, a new registry parameter specific to VLM, tells Oracle Database how much of its address space to reserve for mapping in database buffers. It defaults to a value of 1 GB, which should be suitable for most installations. If DB_BLOCK_SIZE is large, however, the default AWE_WINDOW_MEMORY value of 1 GB may not be sufficient to start the database.
Increasing the value of AWE_WINDOW_MEMORY will improve performance, but it will also limit the amount of memory available for other Oracle Database threads (like foreground threads). Clients may see "out of memory" errors if this value is set too large. As a general guideline, increase the AWE_WINDOW_MEMORY registry value by 20 percent.
For example, if DB_BLOCK_SIZE is set to 8 KB, AWE_WINDOW_MEMORY is set to 1 GB, and the number of LRU latches is set to 32 (16 processor computer), then database startup fails with out of memory errors 27102 and 34. Increasing the value of AWE_WINDOW_MEMORY to 1.2 GB fixes the problem.
Having a large cache in a VLM configuration may also slow down database writer (DBWR) threads. Having more DBWR threads will distribute work required to identify and write buffers to disk and will distribute I/O loads among threads. Initialization parameter DB_WRITER_PROCESSES enables you to configure multiple database writer threads.
A large cache can also introduce contention on the LRU (least recently used) latch. On symmetric multiprocessor (SMP) systems, Oracle Database sets the number of LRU latches to a value equal to one half the number of processors on the system. You can reduce contention on such configurations by increasing the number of LRU latches to twice (or four times) the number of processors on the system.
See Also:
Oracle Database Performance Tuning Guide for more information on instance tuning
Windows 4 GB RAM Tuning (4GT)
The following Windows operating systems include a feature called 4 GB RAM Tuning (4GT):
· Windows Server 2003
· Windows 2000 Advanced Server
· Windows 2000 Datacenter Server
This feature allows memory-intensive applications running on Oracle Database Enterprise Edition to access up to 3 GB of memory, as opposed to the standard 2 GB in previous operating system versions. 4GT provides a tremendous benefit: 50 percent more memory is available for database use, increasing SGA sizes or connection counts.
Large User Populations
Several features allow Oracle Database to support an increasingly large number of database connections on Windows:
· Oracle Database Shared Server Process, which limits the number of threads needed in the Oracle Database process, supports over 10,000 simultaneous connections to a single database instance.
· Oracle Net multiplexing and connection pooling features allow a large configuration to connect more users to a single database instance.
· Oracle Real Application Clusters raises connection counts dramatically by allowing multiple server computers to access the same database files, increasing the number of user connections by tens of thousands, as well as increasing throughput.
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