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PURPOSE
This note discusses the advantages of the 64-bit Oracle architecture.
Oracle 64-bit Advantages:
The key market for 64-bit databases are high-performance systems for applications that
have a very large working data set, and thus can make good use of the improved
memory addressing capabilities of a 64-bit architecture. Using the 64-bit architecture will
also improve scalability and the potential for faster performance offered by the 64-bit
machine. The current 64-bit Oracle release takes full advantage of the latest HP 64 bit
PA-RISC processor technology.
A true 64-bit computing environment has the capability to process 64-bit data,
instructions and addressing. The HP system is a true 64-bit environment, with 64-bit
processor, 64-bit memory addressing capabilities, 64-bit Direct Memory Access (DMA)
and a 64-bit kernel. In a 32-bit system, addressing is limited to 2(32) 32-bit words or 4GB
of memory. With 64 bits we can address 2(64) 64-bit words or 18 billion GB (Exabytes)
of memory, representing a huge increase in the amount of memory that can be
addressed. 64-bit processors achieve better performance by carrying out 64-bit integer
and floating point integer arithmetic operations.
One important advantage of 64-bit memory addressing is the improved scalability of the
machine. Applications can store more data in the larger amount of memory available and
reduce considerably calls to the I/O subsystem. A large SGA is especially useful for
OLTP and applications with a large working data set. More data can be held in memory,
reducing I/O to disks and thereby increasing throughput. In the case of the 32-bit Oracle
database, the amount of System Global Area (SGA), was limited to 1.75GB on 32 bit HP
machines. The SGA for 64-bit Oracle can be grown to occupy all possible physical
memory on a 64-bit system. On HP's largest 64-bit system the physical memory could
be as large as 32GB. A very large memory also allows a greater number of in-memory
processes. The in-memory nature alone is extremely fast. Memory is accessed about
10,000 times faster than disk drives. For large applications that swap to disk frequently,
simply moving to a 64-bit operating environment with generous amount of physical
memory would increase the performance drastically. Such performance improvement is
critical in an e-commerce environment, where there is a large number of connections to
huge databases. With 32-bit HPUX, the limit on the size of the file was 4GB. This
restriction is removed in the 64-bit environment.
The Decision to use 64-bit Architecture:
Before moving to a 64-bit architecture, the Oracle customer should perform a thorough
needs analysis. Here are some issues to consider before moving to a 64-bit architecture:
64-bit computing may not be required everywhere in an environment. For example, in a
three-tier architecture, the back-end database server may be 64-bit, but application
servers and clients can remain 32-bit. Applications that do not require 64-bit features
should remain 32-bit applications.
Scalability on 64-bit machines does not plateau as quickly as 32-bit systems. 64-bit
machines are therefore an ideal choice for applications that require a large amount of
computing power or expect significant future growth and need the scalability of 64-bit
addressability.
32-bit databases run on systems with a small number of 32-bit CPUs (4-6) may see
some degradation in performance if moved to 64-bit systems also with a small number of
64-bit CPUs.
Applications will achieve the benefits of improved scalability on-64 bit machine only if
they are memory intensive. 64-bit applications have bigger data structures because
memory has to be addressed with a larger number of bits. Larger data structures
translate into addtional memory requirements per process.
64-bit systems work more effectively when running with a large number of CPUs.
Oracle produces both 32-bit and 64-bit versions of the Oracle database for HP-UX 11.x.
The 32 and 64-bit versions are built from identical Oracle code. The only difference is the
compile and link time flags. Therefore all features found in a particular version of Oracle
are present in both the 32-bit and 64-bit versions.
The 64-bit version of the Oracle binary supports network connections from both 64-bit
and 32-bit clients.
Running 32-bit Binaries on a 64-bit System:
When running 32-bit Oracle binaries on a 64-bit machine, you will have to set SHMMAX
to 1GB exactly. This is an important requirement when you want to extend the SGA
beyond the 1GB.