Oracle Data Guard - Introduction

Hello,


Introduction to Oracle Data Guard
Oracle Data Guard is most effective and comprehensive data protection and disaster recovery solutions available for enterprise data.
Oracle Data Guard maintains, manages and monitors one or more standby database to protect enterprise data from failures, disasters, errors and corruptions. Standby database is a consistent copy of production database. If the production database becomes unavailable because of a planned or an unplanned outage, Data Guard can switch any standby database to the production role, thus minimizing the downtime and enabling zero data loss.
Data Guard Configuration
1. Primary Database (Production Database)
2. Standby Database
a. Physical Standby database (Redo Apply)
b. Logical standby database (SQL Apply)
Data Guard Services
1. Log Transport Services
2. Log Apply Services : Redo Apply or SQL Apply
3. Role Management Services
Data Guard Broker
Data Guard broker is a distributed management framework that automates and centralizes the creation, maintenance, and monitoring of Data Guard configurations using either GUI (In EM) or CLI(DGMGRL prompt)
Data Guard Protection Modes
1. Maximum Protection: No data loss. Primary database shuts down in case of transmission failure
2. Maximum Availability: No data loss. Primary database tolerates one transmission failure
3. Maximum Performance: A transaction is committed when its redo entries are written to local redo log.
Data Guard and complementary Technologies
1. Oracle Real Application clusters (RAC)
2. Flashback Database
3. Recovery Manager (RMAN)
Summary of Data Guard Benefits
1. Disaster recovery, data protection , and high availability
2. Complete data protection
3. Efficient use of system resources
4. Automatic gap detection and resolution
5. Centralized and simple management
6. Integration with Oracle Database
Types of Standby Databases
1. Physical Standby Databases : It works in 2 modes: Redo Apply ( the database cannot be opened while redo is being applied), open Read only and Open read /write
Although the physical standby database cannot perform both Redo Apply and be opened in read -only mode at the same time, you can switch between them.
Benefits of a Physical Standby Database
1. Efficient disaster recovery and high availability
2. Data Protection
3. Reduction in Primary database workload Performance
2. Logical Standby Database: The logical standby database can be used concurrently for data protection and reporting operations. It has some restrictions on datatypes, types of tables, and types of DDL and DML operations
Benefits of a Logical standby Database
1. It has same benefits as in a Physical standby database
2. Efficient use of standby hardware resources
3. Reduction in primary database workload
Online Redo Logs, Archived Redo Logs, and Standby Redo Logs
Redo data transmitted from the primary database is received by the remote file server (RFS) process on the standby system where the RFS process writes the redo data to archived log files or standby redo log files
Online Redo Logs and Archived Redo Logs
1. Online Redo Logs apply in the primary database and does not apply in the physical standby database
2. Primary database and both physical and logical standby databases each have an archived redo log.
Standby Redo Logs
1. A standby redo log is similar in all ways to an online redo log, except that a standby redo log is used only when the database is running in the standby role to store redo data received from the primary database. It is highly recommended to configure.

Regards,
Sowmya Bandaru (OSR)