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 1 GB exactly. This is an important requirement when you want to extend the SGA beyond the 1 GB.
This was first published in November 2003