To logically partition a database, you first create one or more catalogs.
You can then create one or more schemas in a catalog (although a single schema might be sufficient). If you have multiple schemas, you can specify them either by including the schema as part of the table name, or you can use the SET SCHEMA statement to specify which schema you want to use.
If you do not explicitly CREATE and SET any schema name, then you will use the default schema name, which is your user id.
After you create the catalog and schema, you then create the database objects that will be associated with the schema.