Oracle Database 11g Architecture on Windows Page 6

Much activity has been undertaken to support large numbers of connected database

users on Windows. As far back as Oracle7 version 7.2, there have been customers

in production environments with over 1000 concurrent connections to a single

database instance on Windows NT. As time has progressed, that number has

increased to a point where well over 2000 users can connect concurrently to a

single database instance on a single node in production environments. When using

the Oracle shared server architecture, which limits the number of threads running

in the Oracle database process, over 10,000 simultaneous connections have been

accomplished to a single database instance. In addition, network multiplexing and

connection pooling features can also allow a large configuration to achieve more

connected users to a single database instance.

In recent years, Windows database administrators have been able to further

increase their user counts by employing new 64-bit hardware, either Itanium or

AMD64/EM64T, and Oracle Real Application Clusters (RAC). 64-bit

improvements are discussed later in this paper. Oracle RAC allows multiple server

machines access to the same database files, thereby increasing capacity for user

connections and at the same time increasing throughput as well. Because

commodity hardware can be added as additional nodes to a RAC cluster, RAC has

been a popular solution for cost-effective scaling and high availability. On

Windows, customers have scaled to a 23-node RAC cluster without any issues.

4GB RAM Tuning (4GT)

When clustering and 64-bit Windows are not available options, it is necessary to

maximize the resources available on 32-bit Windows systems. 32-bit Windows

2000 Server (Advanced and Datacenter editions) and 32-bit Windows Server 2003

(Enterprise and Datacenter editions) include a feature called 4GB RAM Tuning

(4GT). This feature allows memory-intensive Windows applications to directly

access up to 3GB of memory as opposed to the standard 2GB that is allowed by

default. The obvious benefit to the Oracle database is that 50% more memory

becomes available for database use, which can be used to increase SGA sizes or

connection counts. All Oracle database server releases since version 7.3.4 have

supported this feature with no modifications necessary to the standard Oracle

installation. The only configuration change required is to ensure that the /3GB flag

is used in the Windows boot.ini file.

Very Large Memory (VLM)

Commonly used in high-memory 32-bit Windows applications is a key memory

tuning feature, originally supported with Oracle8i, called Very Large Memory

(VLM). VLM, available in Windows 2000 and higher, allows the Oracle database

on Windows to break through the 3GB address space limit normally imposed by

32-bit Windows. Specifically, a single database instance can now have access up to

64GB of database buffers when running on a machine and an operating system that

support that much physical memory. This support in Oracle Database 11g is very

tightly integrated with the database buffer cache code inside the database kernel,

The Oracle database on Windows supports

accessing large amounts of memory

through a variety of means, including 4GB

RAM Tuning, Very Large Memory, and

Address Windowing Extensions. Because

Oracle can use the maximum possible

memory, 64GB, on 32-bit Windows, users

experience better scalability and

throughput.