Oracle The Database

Oracle - The Database

The Oracle Database stands for an object-relational database management system or ORDBMS. Oracle came into existing when the three people namely Larry Ellison, Ed Oates and Bob Miner got together to form the Software Development Laboratories company. It was SDL who developed the first version of the Oracle database. Though the name means a Wizard its source was another project Ellison had worked upon while with Ampex.

The Oracle Architecture is comprised of both physical as well as logical structures. Data is stored at the highest level in a Tablespace and traverses down to a Block at the lowest level. A Tablespace is comprised of Extents, an Extent is comprised of Segments, and Segments, in turn, are comprised of Blocks. There are two parts of the entire system – The PGA and the SGA. The PGA is the Process Global Area which is used by the Oracle Client whereas the SGA is the System Global Area used by the Oracle Server. The SGA is home to the Shared Pool which consists of the Library Cache, Data Dictionary Cache and some others as well. The SGA also contains the DBWR and the Large Pool, Java Pool and Stream Pool. Various process are there in the Oracle which helps the logical components interact with the Physical Components. Examples could be the DBW interacting with the Database Buffer and the Data Files, the LGW interacting with the Redo Log Buffer and the Redo Logs on the disk.  A new process has been introduced as the RVWR which interacts with the Flashback Log.