VB+Oracle connectivity

I am a new entrant into the arena of VB+Oracle. Iam currently using VB6 with Personal Oracle8 and have set up the database conectivity using an ODBC DSN.
I want to provide a search facility in the frontend.Using Find method is too slow,as I expect to have alarge database in the backend.Pl give tips for setting up search.
Also in the backend database,I have a table in which certain records or certain fields are blank.They give me problems when using navigation buttons set on the frontend side form.Though the Navigator shows the 'Not Null' property set up for the fields.