R

RAR file

A Resource Adaptor Archive file. By convention, the extension given to Jar files that contain JCA resource adaptors.

RDBMS

Acronym for relational database management system, also called a relational database or SQL database.

Relational model

The logical arrangement of persistent state in the relational database. The relational model in a relational database defines, among other things, the names and types of the columns, the names of the tables, the columns in the tables, and the relationships between the tables.

Results collection

The Collection of objects returned from the Query object's execute method. The objects in the collection are all members of the query's candidates, which is either an Extent or a Collection. They are all assignment compatible with the query candidate class. For each of them, the query filter evaluates to true when using the values of parameters, if any, that are passed to the execute method.

Rollback

An operation that ends a transaction by asking the transactional service to reject all changes made within the transaction. When the rollback is successful, the service rejects all changes. Rollback fails only when the connection to the service fails. In this case, the service itself will eventually roll back the transaction.