An Oracle database system is identified by an alphanumeric system identifier. SID comprises at least one instance of the application, along with data storage. Typical processes include PMON and SMON. Oracle documentation can refer to an active database instance as a "shared memory realm". Users of Oracle databases refer to the server-side memory-structure as the SGA. The SGA typically holds cache information such as SQL commands, data-buffers, and user information.
The database consists of online redo logs, which hold transactional history. Processes can in turn archive the online redo logs into archive logs which provide the basis for data recovery. It is for the physical-standby forms of data replication using Oracle Data Guard. The advantage of Oracle RAC is that the resources on both nodes used by the database. Each node uses its own memory and CPU. Information is shared between nodes through interconnect the virtual private network.
The Oracle DBMS can store and execute stored procedures and functions within it. PL/SQL or the object-oriented language Java can invoke such code objects provide the programming structures for writing them.