Introduction Oracle Data Guard is one of the software solutions provided by Oracle Corporation to maximize high availability of Oracle databases. Oracle Data Guard maintains one or many secondary databases as alternatives to the primary production database. Data Guard Architecture Oracle Data Guard supports both physical standby and logical standby sites. Physical Standby: When the primary database transactions generate redo entries, a redo apply process keeps up the secondary databases with the exact block copies of the primary database. Logical Standby: SQL apply processes read the redo and convert it to SQL transactions. These are then applied to the secondary database. Active Data Guard is an option license for Oracle Database Enterprise Edition. Active Data Guard enables. On an active standby; Active Data Guard Rolling. Activating Standby Database (failover). And activate the standby database. What happens when the Oracle standby database is activated to become a primary. Jul 02, 2015 This blog is to help online community using Oracle database. I share my Oracle knowledge through this blog. All my posts in this blog are based on my. Data Guard Modes Oracle Data Guard can operate in 3 different modes: • Maximum Protection: Transactions are not allowed to commit until all redo data are written to the online redo logs and propagated to at least one synchronized secondary database. If for any reason, the primary database cannot propagate its redo stream to one secondary database, the primary will shutdown to ensure maximum protection mode. • Maximum Performance: Transactions are not allowed to commit as soon as the redo are written to the online redo logs. The redo stream is asynchronously propagated to the secondary databases to ensure maximum performance mode. • Maximum Availability: Transactions are not allowed to commit until all redo data are written to the online redo logs and propagated to at least one synchronized secondary database. If for any reason, the primary database cannot propagate its redo stream to one secondary database, the primary will NOT shutdown and operates as it it were in maximum performance mode until issues are fixed. Glossary • Role transition: Changing the role of each database component from primary database to the secondary database or from secondary database to the primary database. • Switchover: Planned role transition for testing. Manual intervention. • Fail Over: Unplanned failure. Manual or Automatic intervention. Automatic role transition is the recommended. • Primary database: Where the users are connected to access to the database. • Standby database: Exists in the the disaster recovery (DR) site. Where the users are connected in the case of planned role transition (Switchover) or in the case of unplanned failure (Fail Over). • Data Guard Observer: Process monitors both primary and standby databases and performs an automatic fail over when necessary.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
March 2018
Categories |