How can I import the contents of an Oracle database into Visio to create an Entity Relationship Diagram?
All you need is configured ODBC connection to Oracle DB


1. Install Oracle Client SW (download from otn.oracle.com). I recommend installing same version as your Oracle DB
2. Define connection in tnsnames.ora
3. Create and test ODBC connection to Oracle DB in Control Panel > Administrative Tools > Data Sources (ODBC) -  use Oracle's driver in your ORA_HOME, use connection defined in tnsnames.ora
4. Importing from defined ODBC connection to Oracle should be same as importing from Access DB