Explore Oracle 11g elastic uard

1. What is Alibaba uard?

DataGuard is a high-availability technology specifically designed for Oracle databases launched by oracle. It was called Standby Dtabase before 8i and officially changed its name from 9i to DataGuard. Generally, there are at least two data image nodes in the master-slave relationship. The redo log synchronization technology can be used to ensure real-time data synchronization, And the Master/Slave database can be quickly switched to implement data disaster tolerance.

2. Why should I use javasuard?

DataGuard, also known as data guard, is a technology launched by ORACLE to ensure data security. It is mainly used for some occasions with high importance on data security, such as banking, in the telecom and other industries, they have applied a large number of consumer uard data guards to ensure data security.

Of course, it is also used for routine database maintenance without interrupting services, such as routine downtime, test changes, upgrade and maintenance, etc.

3. value brought by DataGuard

Zero data loss and zero downtime can be achieved to ensure the continuous online operation of services. The database pressure can be effectively shared through read/write splitting to reduce the risk of downtime for various reasons.

4. Architecture of DataGuard

5. Secure uard

DataGuard synchronization is implemented through redo transmission and data synchronization on standby applications. Therefore, its synchronization link is built on Oracle Net and is used for data transmission through Oracle Net, it uses the SSL protocol. SSL uses RSA public key and symmetric key encryption to provide authentication, encryption, and data integrity. SSL is automatically used for redo transport verification in two Oracle databases. If the SSL authentication requirement is not met, each database must use a remote login password file. In a replicasuard configuration, all physical and snapshot backup databases must use a copy of the password file from the master database. Refresh the copy must be granted or revoked by the SYSOPER or SYSDBA privilege, any user's password and these privileges are changed

When a password file is used for redo transmission verification, the user account in the password file is used for redo transmission between databases to start a redo transmission session and the target database. The password must be in the same two databases. By default, the System user password is used to verify the redo transport session password file.

6. Three protection modes of DataGuard

Maximum protection mode:

1) This mode provides the highest level of data protection capabilities;
2) requires at least one physical standby database to submit the transaction of the primary database after receiving the redo log;
3) when the primary database cannot find a suitable standby database for writing, the primary database will be automatically disabled to prevent unprotected data;
4) Advantage: This mode ensures that no data is lost in the slave database;
5) Disadvantages: the automatic shutdown of the master database will affect the availability of the master database. At the same time, the slave database must be restored before submission. The network and other objective conditions are extremely demanding, the performance of the master database is greatly affected.

Maximum availability mode:
1) This mode provides data protection capabilities second only to the "maximum protection mode;
2) requires at least one physical standby database to submit the transaction of the primary database after receiving the redo log;
3) when the primary database cannot find a suitable standby database for writing, the primary database will not be closed, but will be temporarily reduced to the "maximum performance mode" mode until the problem is solved;
4) Advantage: This mode ensures that no data is lost in the slave database when no problem occurs;
5) Disadvantages: The disadvantage during normal operation is that the performance of the master database is affected by many factors.

Maximum performance mode:
1) This mode is the default mode to ensure the highest availability of the primary database;
2) Ensure that the master database is not affected by the slave database during operation, the master database transactions are committed normally, and the operation of the master database is not affected due to any problems of the slave database;
4) Advantages: This avoids the impact of the slave database on the performance and availability of the master database;
5) Disadvantages: If the recovered data related to the transaction committed by the master database is not sent to the slave database, the transaction data will be lost, and no data loss can be guaranteed;

For more information about Oracle 11g replicuard configuration, see

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