Monitoring High Availability Disaster Recovery environment in DB2 UDB Enterprise Edition
The High Availability Disaster Recovery (HADR) database replication feature provides a high availability solution for both partial and complete site failures. HADR prevents data loss by replicating updates from a source database (called the primary database) to a target database (called the standby database).
Applications can only access the current primary database. Updates to the standby database occur by rolling forward log data that is generated on the primary database and transferred to the standby database.
With HADR, you can select the level of data protection by specifying one of the following synchronization modes:
- Synchronous
- Near synchronous
- Asynchronous
After the failed primary server is repaired, it can rejoin the HADR pair as a standby database if the two copies of the database can be made consistent. After the original primary database is reintegrated into the HADR pair as the standby database, you can switch the roles of the databases to enable the original primary database to again be the primary database.
Based on the data returned by the db2 get snapshot command for database, if the role is primary, the DB2DB_HADR application class is automatically discovered by PATROL for DB2 Universal Database. The DB2DB_HADR application class is available under the DB2_DB/ databaseName icon, and its parameters are online. The InfoBox for that database reflects the database status as ACTIVE.
If the role is standby, the DB2_DB/ databaseName icon is offline. The InfoBox for that database reflects the database status as STANDBY.
The failover from primary to standby and vice versa is automatically detected by PATROL for DB2 Universal Database.
This section presents the following topics: