What is the difference between dg and adg in oracle

Difference: 1. dg refers to Data Guard data guard, which has the backup function and can ensure the high availability and data protection of data. adg is "Active Data Guard", which can query or export data and is suitable for Read-only application; 2. dg reading and writing cannot be parallel, but adg reading and writing can be parallel.

The operating environment of this tutorial: Windows 10 system, Oracle 11g version, Dell G3 computer.

What is the difference between dg and adg in oracle

DG (Data Guard)

DG (Data Guard, Data Guard) is not a backup and recovery Tools, however, DG has a backup function. It can be exactly the same as the main database under physical DG, but its purpose of existence is not just to backup and restore data. It should be said that its existence is to ensure the high availability of enterprise data. Data protection and disaster recovery. DBA can reduce the pressure on the main database and build a highly available enterprise database application environment by transferring some operations (such as query reports) to the standby database for execution.

In the DG environment, there are at least two databases, one of which is in OPEN state and provides external services. This database is called the Primary Database. The second one is in recovery state and is called Standby Database. Under normal circumstances, the main database provides services to the outside world, and users perform operations on the main database. The operations are recorded in online logs and archive logs. These logs are transmitted to the standby database through the network, and then applied on the standby database, thereby realizing the primary database. Data synchronization between database and standby database.

Oracle has further optimized the design of this process, making the log delivery and recovery work more automated and intelligent, and provides a series of parameters and commands to simplify DBA work. If the software and hardware are upgraded, the standby database can be switched to the primary database to continue external services. This reduces the service downtime and prevents data loss. If the main database is unavailable due to abnormal reasons, the standby database can also be forced to switch to the main database to continue external services. In this case, the data loss is related to the configured data protection level. Therefore, Primary and Standby are just role concepts and are not fixed in a certain database.

adg

Before Oracle 11g, the physical standby could not be opened when redo was applied, but could only be mounted. Starting from 11g, when applying redo, the physical standby database can be in read-only mode, which is called Active Data Guard. Through Active Data Guard, you can query or export data in the physical standby database, thereby reducing access and pressure on the primary database.

Active Data Guard is suitable for some read-only applications. For example, some applications only query data and perform some reporting services without generating redo data. These applications can be transferred to the standby database to avoid redo data. Contention for master library resources.

ADG mainly solves the problem of parallel reading and writing in the DG era.

If the data synchronization method in the DG era adopts the physical method of Redo Log, the database will synchronize data quickly and The resource consumption is low, but there is a big problem.

The Data Guard physical backup database before Oracle 11G can open the data in read-only mode, but the data synchronization process of the log stops at this time. If the data synchronization of the log is in progress, the database cannot be opened. That is to say, the two states of log reading and writing are mutually exclusive. Active Data Guard mainly solves this problem.

Oracle has the function of flashback database to avoid irreversible misoperations such as table deletion

When the main database is open and active, the transaction is in the processing state and generated Redo Log data and transfer it to the standby database. Under normal circumstances, data synchronization can be achieved in seconds. However, if an incorrect command is executed on the primary database, such as drop database, all data in the standby database will also be deleted.

Oracle DG provides an easy-to-use way to avoid this user error. DBA can use the flashback database function in the primary database and standby database at the same time to quickly restore the database to an earlier point in time, thereby canceling this misoperation.

In addition, Oracle also provides the function of delayed backup database synchronization, which is another way to prevent misoperation.

Recommended tutorial: "Oracle Video Tutorial"

The above is the detailed content of What is the difference between dg and adg in oracle. For more information, please follow other related articles on the PHP Chinese website!