I want to rename an assembly, but i lost all the feature part references. For example, i have the assembly file 01xxx_000_000_A and i want to rename it in 01999_000_000_A. I can do this with the save as command. Now i can open the assembly 01999_000_000_A and solidworks find all the parts that are be connected with this assembly. Only the features of the parts reference of 01xxx_000_000_A shown up in the featuremananger with e.g. Cut-Extrude1->? I think that i do something wrong. Can anybody help me out to do this the correct way.
What you are saying is correct for the method applied to saving a new assembly (i.e. the original part features are in context of the original assembly). If you want part features to be in context of the new assembly you must assign new part file names when saving the assembly. There are a couple of methods to do this (a) when saving the new assembly click on Reference button, assign new part file names and locations if desired (b) use SolidWorks Explorer to create new assembly and assign new part file names.
This whole file managing thing can be quite confusing as there are so many ways and choices along the way. I still get confused Also, there is additional information in SolidWorks Help or try experimenting yourself on an assembly to learn how SolidWorks manages these files. For myself, I created a three piece assembly of simple blocks and then experimented with the different ways of saving assemblies. There is probably one method you will not want to employ. That is saving a new assembly, clicking on Reference button and checking off the box next to each existing filename. Yes, it will create new part files in context of the new assembly, but these new parts share the same filenames with original assembly. Not a good thing to do as you know.