Administration Servers Role in Whole Server Migration Migratable Server Behavior in a Cluster

High Availability for WebLogic Server 3-11 Figure 3–3 Manual Whole Server Migration

1. An administrator uses the Administration Console to initiate the migration of

Managed Server 2 from Machine C to Machine B.

2. The Administration Server contacts Node Manager on Machine C. See

Section 3.9.2.4, Administration Servers Role in Whole Server Migration.

3. Node Manager on Machine C stops Managed Server 2.

4. Managed Server 2 removes its row from the lease table.

5. The Administration Server invokes Node Manager on Machine B.

6. Node Manager on Machine B starts Managed Server 2.

7. Managed Server 2 obtains its configuration from the Administration Server.

8. Managed Server 2 caches the configuration it started up with.

9. Managed Server 2 adds a row to the lease table.

3.9.2.4 Administration Servers Role in Whole Server Migration

In a cluster that contains migratable servers, the Administration Server invokes Node Manager on each system: ■ That hosts cluster members to start the migratable servers. This is a prerequisite for server migratability—if Node Manager did not initially start a server instance, you cannot migrate the server. ■ Involved in a manual migration process to stop and start the migratable server. 3-12 Oracle Fusion Middleware High Availability Guide ■ That hosts cluster members to stop server instances during a normal shutdown. This is a prerequisite for server migratability—if a server instance is shut down directly without using Node Manager, when the cluster master detects that the server instance is not running, it will call Node Manager to restart it. The Administration Server also provides its regular domain management functionality, persisting configuration updates issued by an administrator and providing a run-time view of the domain, including the migratable servers it contains.

3.9.2.5 Migratable Server Behavior in a Cluster

A migratable server is a clustered Managed Server that is configured as migratable. These are the key behaviors of a migratable server: ■ If you are using a database to manage leasing information, during startup and restart by Node Manager, a migratable server adds a row to the lease table. The row for a migratable server contains a timestamp, and the machine where it is running. ■ When using a database to manage leasing information, a migratable server adds a row to the database as a result of startup, it tries to take on the role of cluster master, and succeeds if it is the first server instance to join the cluster. ■ Periodically, the server renews its lease by updating the timestamp in the lease table. By default a migratable server renews its lease every 30,000 milliseconds—the product of two configurable ServerMBean properties: – HealthCheckIntervalMillis, which by default is 10,000. – HealthCheckPeriodsUntilFencing, which by default is 3. ■ If a migratable server fails to reach the lease table and renew its lease before the lease expires, it terminates as quickly as possible using a Java System.exit—in this case, the lease table still contains a row for that server instance. For information about how this relates to automatic migration, see Section 3.9.2.7, Cluster Masters Role in Whole Server Migration. ■ During operation, a migratable server listens for heartbeats from the cluster master. When it detects that the cluster master is not sending heartbeats, it attempts to take over the role of cluster master, and succeeds if no other server instance has claimed that role.

3.9.2.6 Node Managers Role in Whole Server Migration