Multiple standby databases
DB2 high availability disaster recovery (HADR) configuration is used to provide continuous data availability to all the IBM Security Key Lifecycle Manager instances in a Multi-Master cluster. HADR protects against data loss by transmitting data changes from a source database, called primary, to a target database, called the standby.
DB2 HADR supports three standby databases in your Multi-Master setup, one standby for high-availability and other two standbys for disaster recovery. When the primary database is down, The HADR takeover service instructs the standby database to take over as a new HADR primary database. For more information about HADR takeover service, see HADR takeover service.
Priorities are assigned to each of the standby database in the cluster. Standby with the higher priority is the one that assumes the primary database role. For example, if a primary database in the IBM Security Key Lifecycle Manager Multi-Master cluster fails, the standby database with a priority index 1 takes over the role of the primary database.
To add multiple standbys to the cluster, you can use IBM Security Key Lifecycle Manager graphical user interface or Add Master REST Service. For more information, see Adding a standby master to Multi-Master cluster.
HADR takeover scenarios
| Primary Database Host System Agent | Primary Database | Standby 1 Database Host System Agent | Standby 1 Database | Standby 2 Database Host System Agent | Standby 2 Database | Standby 3 Database Host System Agent | Standby 3 Database | Agent Actions | IBM Security Key Lifecycle Manager Key Serving | Auto Takeover |
|---|---|---|---|---|---|---|---|---|---|---|
| Up | Up | Up | Up | Up | Up | Up | Up | Happy scenario. | From primary database | NA |
| Up | Up | Up | Down | Up or Down | Up or Down | Up or Down | Up or Down | - | From primary database | NA |
| Up | Up | Down | Down | Up or Down | Up or Down | Up or Down | Up or Down | - | From primary database | NA |
| Up | Down | Up | Up | Up or Down | Up or Down | Up or Down | Up or Down | Agent on primary sends request to agent on standby 1 server to takeover as primary database. | From standby 1 database | Yes, if primary or standby 1 database, whichever is available for takeover, and agents on both the servers must be running and can communicate with each other. Else, No. |
| Down | Down | Up | Up | Up or Down | Up or Down | Up or Down | Up or Down | - | From standby 1 database | No |
| Up | Down | Up or Down | Down | Up | Up | Up or Down | Up or Down | Agent on primary sends request to agent on standby 2 server to takeover as primary database. | From standby 2 database | Yes, if primary or standby 2 database, whichever is available for takeover, and agents on both the servers must be running and can communicate with each other. Else, No. |
| Down | Down | Up or Down | Down | Up or Down | Up | Up or Down | Up or Down | - | From standby 2 database after manual takeover | No |
| Down | Down | Down | Down | Up or Down | Up | Up or Down | Up or Down | - | From stand by 2 after manual takeover | No |
| Up | Down | Up or Down | Down | Up or Down | Down | Up | Up | Agent on primary sends request to agent on standby 3 server to takeover as primary database. | From standby 3 database | Yes, if primary or standby 3 database, whichever is available for takeover, and agents on both the servers must be running and can communicate with each other. Else, No. |
| Up | Down | Up or Down | Down | Up or Down | Down | Up or Down | Down | - | None | No |