Using hashfiles from Datastage version 4

[ray.wurlod]

There are absolutely no problems. There is nothing different in how hashed files are implemented by default between release 4.0 and release 6.0.
Release 6.0 has extra features, as does release 5.x, such as your being in better control of memory caching, and the hashed file stage having the ability to specify the size and shape of the hashed file (instead of accepting the default, which you were doing in release 4.0), but all of these things are extras; the underlying hashed file technology is unchanged.