Database migrations from an 32bit environment to an 64bit environment keeping the same platform architecture (e.g. moving an Oracle 10.2.0.5 database from MS Windows XP 32bit to MS Windows Server 2003 64bit) does not happen that often anymore. But still we see them getting done. And there are a few things to note when doing such a move.

First of all the important question is:
Will you upgrade your database as part of this move - Yes or No?

If you say "Yes" then you are almost done with that topic as we will take care of that bitnes move during the upgrade. The only thing you have to take care is OLAP in case you are using OLAP Option with Analytic Workspaces (AW) by yourself. Those store data in Binary LOBs - and in order to move AWs from 32bit to 64bit you have to export your AWs prior to the move - and import them later on. People who don't use OLAP don't have to take care on this.

But if you say "No" (meaning: no upgrade actions involved - you keep your database version) then you have to make sure to invalidate all packages and stored code in the database before you shutdown your database in the 32bit environment and prior to moving it over. And the same rule as above for OLAP applies once you use the OLAP Option.

In the source environment:

startup upgrade;    -- [or startup migrate; -- for Oracle 9i]
@?/rdbms/admin/utlirp.sql
shutdown immediate

In the destination environment:

startup upgrade
@?/olap/admin/xumuts.plb --Only if OLAP Option is installed
@?/rdbms/admin/utlrp.sql

The script utlirp.sql will invalidate all packages and stored code, utlrp.sql will recompile - and xumuts.plb will rebuild the OLAP Analytic Workspaces in case you have the OLAP Option installed.