Machine C, which hosts Managed Server 2, fails. Upon its next periodic review of the lease table, the cluster master detects that

High Availability for WebLogic Server 3-9 5. Managed Servers 1 and 2 cache the configuration they started up. 6. Managed Servers 1 and 2 each obtain a migratable server lease in the lease table. Because Managed Server 1 starts up first, it also obtains a cluster master lease. See Section 3.9.2.7, Cluster Masters Role in Whole Server Migration. 7. Managed Server 1 and 2 periodically renew their leases in the lease table, proving their health and liveness.

3.9.2.2 Automatic Whole Server Migration Process

Figure 3–2 illustrates the automatic migration process after the failure of the machine hosting Managed Server 2. Figure 3–2 Automatic Migration of a Failed Server

1. Machine C, which hosts Managed Server 2, fails.

2. Upon its next periodic review of the lease table, the cluster master detects that

Managed Server 2s lease has expired. See Section 3.9.2.7, Cluster Masters Role in Whole Server Migration. 3-10 Oracle Fusion Middleware High Availability Guide 3. The cluster master tries to contact Node Manager on Machine C to restart Managed Server 2, but fails, because Machine C is unreachable. 4. The cluster master contacts Node Manager on Machine D, which is configured as an available host for migratable servers in the cluster. 5. Node Manager on Machine D starts Managed Server 2. See Section 3.9.2.6, Node Managers Role in Whole Server Migration. 6. Managed Server 2 starts up and contacts the Administration Server to obtain its configuration. 7. Managed Server 2 caches the configuration it started up with. 8. Managed Server 2 obtains a migratable server lease. During migration, the clients of the migrating Managed Server may have a brief interruption in service; it may be necessary to reconnect. On Solaris and Linux operating systems, you can reconnect using ifconfig command. The clients of a migrated server do not need to know the particular machine the server migrates to. When a machine that previously hosted a server instance that was migrated becomes available again, the reversal of the migration process—migrating the server instance back to its original host machine—is known as failback. WebLogic Server does not automate the failback process. An administrator can accomplish failback by manually restoring the server instance to its original host. The general procedures to restore a server to its original host are: ■ Gracefully shutdown the new instance of the server. ■ After you restart the failed machine, restart Node Manager and the managed server. The exact procedures you follow depend on your server and network environment.

3.9.2.3 Manual Whole Server Migration Process