Oracle/Database/Oracle Client

32bit and 64bit
Source: Considerations Using The Oracle Client With Microsoft Products on 64 bit Operating System [ID 781432.1]

The Oracle Client Install

64 bit applications require 64 bit Oracle Client software, and 32 bit applications require 32 bit Oracle client software. Oracle does not currently provide a single bundle that will install both 32 bit and 64 bit Oracle client, so in order to run both 32 bit and 64 bit applications on the same operating system both 32 bit and 64 bit Oracle client software will need to be installed as separate steps, and the installs need to go into separate Oracle homes. 32 bit installation and 64 bit installation are not aware of each other, and as with all multiple home installations the TNSNames.ora in both homes will need to be updated with the connect information, or TNS_ADMIN environment variable set. The 32 bit Oracle Universal Installer will only show information on the 32 bit home, and the same with 64 bit. Please note: that there is currently an issue where installing both 32 bit and 64 bit client on the same box will cause the second installation to overwrite the Start Menu shortcuts of the first installation if separate Oracle Home names are not used. 11.2 does not give you the opportunity to set the Oracle Home names via the OUI, but you can pass it as a command line argument setup.exe ORACLE_HOME_NAME=OraHome11g_client64 for example. When installing both 32 bit and 64 bit Oracle client software onto a single box, both Oracle homes will need to be in the PATH environment variable, although the order is not important. The Oracle home information is stored in the registry as follows, which can be used to infer whether 32 bit or 64 bit Oracle client software is installed. -The 64 bit Oracle home will be setup in the registry in the following location: HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE - The 32 bit Oracle home will be setup in the registry in the following location: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\ORACLE Earlier versions of Oracle client software had a known bug that resulted in a ora-6413 or ora-12154 when an application was run from a path containing parenthesis, which is the default location for installation of 32 bit applications on a 64 bit operating system - Program Files (x86). Applying the latest patches to the client install should resolve this issue. For more information refer to Note.334528.1.