Explain the relationship among database, tablespace and data file.
Here is the answer of your question,
Database : Database is the Collection of data is called database.
Table Space : The table space is useful for storing the data in the database. When a database is created two table spaces are created.
1-System Table Space
: This data file stores all the tables related to the system and dba tables.
2-User Table Space
: This data file stores all the user related tables. We should have separate table spaces for storing the tables and indexes so that the access is fast.
Data Files : Every Oracle Data Base has one or more physical data files. They store the data for the database. Every data-file is associated with only one database. Once the Data file is created the size cannot change. To increase the size of the database to store more data we have to add data file.