The Oracle9i data guard architecture consists of the following components:

  • Primary database - The first component of the Oracle data guard architecture is the primary database. The primary database is the database that you want to protect from failure and disaster. To use data guard, the primary database must be in ARCHIVELOG mode.
     
  • LGWR process - The LGWR process can be used in Oracle9i to move database redo in certain cases, to the standby database.
     
  • Log transport services - This component previously existed as a part of the RDBMS in standby database configurations in Oracle8i. It has been separated in the standby database architecture, allowing for additional functionality.
     
  • Oracle Net - Oracle Net is the Oracle networking facility formally called Net8. This networking architecture can be used to facilitate the movement of generated redo from the primary database to the standby databases.
     
  • Standby database(s) - Oracle's standby database architecture is for environments that require quick recovery from failure.
     
  • Log application services - The log application services are used to manage the standby database in various recovery modes.

The relationship of these different components is illustrated in the Figure 1 below.

Figure 1 - Oracle Data Guard Architecture

The remainder of the topics in the Data Guard section explore these components in greater detail.