For a domino server the requirement is to install the 64 bit code, and then move your Notes applications to the server.  If you have a specific coed which is in 32 bit, and you have tested and it will not operate in a 64 bit environment, you will nee to recompile the code using a 64 bit compiler

The 32-bit code does not work in the 64-bit domino server environment. We tried to recompile the code via Visual Studio and received quite a few errors, e.g. No platform specified; Cannot open include file: 'global.h': No such file or directory; etc.  Any advise on how to resolve these issues? Thanks.

1. You have to recompile your code to run it on 64-bit Domino. That may or may not be a trivial process. See here for some pointers.
2. Continue running a 32-bit version of Domino, preferably as a bridge while the work to update it for 64 bit is underway.

Check out the presentation below.  I used it while researching an upgrade deployment from Win Server 2003 32-bit to Win Server 2012 R2 x64 boxes that also would involve transitioning to Domino 9.

BP 102: IBM Domino 64bit - All You Need to Know
http://www.nashcom.de/nsh/web.nsf/ff5ce882e73ab026c1256942003bdf10/6084a81e9f2c2b00c1256cc30030c6c1/$FILE/bp102.pdf

We too had some 32-bit tasks running on Domino that I could find no way to port (not ours; a vendors...).  Ultimately, the above convinced me that, currently, the 64-bit OS provides the majority of the benefit, even when running 32-bit Domino.  Note the quote on page 10 of the presentation: "Running 32Bit Domino on 64bit OS gives you already most of the performance and scalability benefits."

I've not been disappointed.  The 30+ Domino EXEs now have up to 4GB each to expand into instead of sharing that 4GB on the Win 2003 server (I can't believe we were actually surviving before on a 4GB server...).

The Domino processes typically consume 8-12 GB RAM (out of 32GB) with no one process running beyond 0.8-0.9GB.  Traveler, ScanMail for Domino from Trend Micro, and HTTP are typically top memory consumers, followed by nserver and several nupdate tasks.  We have a couple of 8-10GB databases with > 1-mil docs each and dozens of views, which probably accounts for the nupdate tasks being so high on the memory usage, at about 0.67GB each.

I will probably transition to 64-bit Domino at some point in the future, but 32-bit Domino on 64-bit OS has, so far, provided the performance boost and headroom needed right now while giving time to figure out how to either deal with 32-bit compatibility issues or find a replacement for what they do.

Thanks, Mark, for the comment. 64-bit Domino is the global standard that we have to follow even though quite a few existing 32-bit tools could not run well on it.