> If I use stored vimobjectRef, how can I construct object from that?
You can't. You need to persist the object data not the reference.
> Based on the UI query, If i try to create objects and load all the objects,then i assume it will slow down the ui.
Your data adapter doesn't know and doesn't care where the query comes from and how the data is used by the UI. It's only job is to return data based on the querySpec parameter.
> Can I create an Object which can be recognized by VCener Server and vSphere UI using a data from the DB.
Data adapters are for returning data to the UI. I am not sure what you mean by "recognized by vCenter server". vCenter only manages vSphere objects, not custom objects like the chassis and racks of the SDK sample.
It looks like you are still confused about the Web Client architecture. Have another look at the Programming Guide PDF and the HTML docs in the SDK. Run the samples while setting break-points in the service and data adapter code to understand what happens.