Hi, here is from IBM.
I need to recompile it for 64 bit platforms.
Question: What things do I need to consider before I deploy 64-bit Domino?
Answer: You must have 64-bit hardware and it must be running a supported 64-bit OS (see the first question/answer above for a list of supported platforms). You must obtain 64-bit Domino related software (for example, addins, backup software, anitvirus, and so on) and not just 64-bit Domino. You cannot use 32-bit Domino related software with 64-bit Domino. Only 64-bit addins and Domino related software can be run with 64-bit Domino. For example, you will need a 64-bit version of LSX, where there are shared libraries. You will need 64-bit versions of Sametime and Quickr when they become available. Not all third party products support 64-bit yet, so be sure to check with the third party vendor.
You need to review your existing Domino applications. Existing databases and Java and LotusScript agents within Domino will continue to run successfully. Any C API applications (Domino server addins and extension manager DLLs) will need to be rebuilt (compiled and linked), however.