The 32- vs. 64-Bit Oracle Debate

Another issue that gets a lot of attention is whether you should run 32-bit or 64-bit Oracle on your 64-bit UNIX. At first this sounds like a dumb question, right? But for some of the platforms, the answer may very well surprise you. For example, Oracle's Metalink technical support site quotes that:

  • 32-bit Oracle on HP-UX 11.00 32-bit?No difference

  • 32-bit Oracle on HP-UX 11.00 64-bit?1?2% degradation

  • 64-bit Oracle on HP-UX 11.00 64-bit?8?9% degradation

And here I thought that 64-bit was always faster. The point is: Know your target platform and its Oracle ports. Don't just assume that bigger is better.

Then there's the ever-popular question of the maximum system-wide SGA size limit of 32-bit versus 64-bit Oracle. For example, with 32-bit Oracle, the maximum system-wide SGA size limit is 1.75 GB for HP-UX (or, when using memory windows, 1 GB per instance with another .75 shared system-wide) and 3.75 GB for Solaris. But with either of these operating systems running the 64-bit version of Oracle, the maximum system-wide SGA size is limited only by the physical amount of memory present on the machine.

Finally, there's the new version and patch issue again. Oracle historically released the 32-bit versions first. But now, Oracle seems fully committed to doing the 64-bit versions first, with some platforms no longer even offering 32-bit versions. Again, you need to know your target platform and its Oracle ports.

If you've accepted the prior recommendation for Sun hardware, there is a clear answer: 64-bit Oracle all the way. On Sun Solaris, 64-bit Oracle is faster than the 32-bit version?you'll need those very large SGAs for good I/O performance?and remember, new releases and patches come out on Sun first. Plus, 64-bit on Sun is the only version now supported.