DBAs often need to know if they should install Oracle 32-bit or 64-bit software on a given server. If the operating system support 64-bit applications, the 64-bit Oracle distribution can be loaded. Otherwise, the 32-bit distribution must be installed. The following Unix commands will tell you whether your OS is running 32-bits or 64-bits:
Solaris - isainfo -v (this command doesn't exist on Solaris 2.6 because it is only 32-bits)
HP-UX - getconf KERNEL_BITS
AIX - bootinfo -K
If you need to know if Oracle 32-bit or 64-bit software is currently installed on a system, connect using a command line utility like sqlplus and look at the banner. If you are running 64-bit software, it will be mentioned in the banner. If nothing is listed, you are running on a 32-bit base.