Oridinarily you will not need to specify the schema and in fact, when using
JDBC I believe that some DBMS's have support for a schema name in JDBC URLs. Note that I am talking generically, Your Mileage May Vary.
The default schema is conventionally named "default" as I recall. You do not need to include it as part of a table identification unless you are currently running out of some other schema.
As a general rule, you'll always be working with the default schema. Alternative schemas would be for exceptional situations where, perhaps a number of clients shared distinct sets of tables in a single database or you were prototyping a new or legacy version of a schema.
Finally, note that "schema" is both a specific database entity type (for databases that support them) and a generic description of the user-visible architecture of a database, Don't confuse the two.
Also, since things do vary, I'd recommend specifically looking in the Oracle documentation for their definition of "schema".
