Applying the Changes Made to the Model

The latest version of the model describes the desired structure of a grid, not its current structure. Any changes made to the latest version of the model are not immediately reflected in the operational configuration of a grid. Changes made to the latest version of the model need to be explicitly applied to the grid.

Model Versioning

Management instances store multiple versions of the model. Only one version of the model can be active in the grid at any given time.

TimesTen Scaleout classifies model versions as follows:

• Current version: The current version of the model describes the operational configuration of the grid. This version, and all previous versions, is read-only.

• Latest version: The latest version of the model can be modified and has yet to be applied to the grid. This version is read/write.

When you create a grid, the version 1 model is initially populated with the configuration of the first host, installation, and management instance, and the version 1 model is recognized as the latest version of the model. Any subsequent changes that you make to the model are added to the latest version of the model (version 1). When you implement these changes with the ttGridAmin modelApply command, a new latest version of the model (version 2) is created for future changes and the previous latest version of the model (version 1) becomes the current version of the model.

Every time you run the ttGridAdmin modelApply command, TimesTen Scaleout:

1. Makes the latest version of the model (version n) read-only.

2. Creates a writable copy (version n+1) of the latest version of the model.

3. Attempts to apply the changes previously made to the version n model to the operational grid.

4. Identifies the version n model as the current version of the model.

5. Identifies the version n+1 model as the latest version of the model.

The ttGridAdmin utility enables the user to perform several operations regarding the model, like:

• Applying the changes made to the latest version of the model

• Comparing two versions of the model

• Exporting a version of the model into a flat file in JSON format

• Importing a flat file in JSON format as the latest version of the model

• Listing all the available versions of the model

Previous versions of the model are automatically stored. With the ttGridAdmin gridModify command, you can specify the retention period for old versions of the model either in terms of days, in terms of the number of stored versions, or both. TimesTen Scaleout by default retains the last 10 versions for a period of 30 days.

For more information on model operations or the ttGridAdmin gridModify utility, see Model Operations or Modify Grid Settings (gridModify), respectively, in Oracle TimesTen In-Memory Database Reference.

Apply the Latest Version of the Model

The ttGridAdmin modelApply command attempts to apply the changes made to the latest version of the model into the operational grid. If, for example, you add a new data instance to the latest version of the model, running this command performs all of the necessary operations to create and initialize the instance in the specified host. Some of the operations that the ttGridAdmin modelApply command performs include these:

• Identify and delete any object removed from the latest version of the model.

• Create new installations.

• Create new instances, data and management.

• Overwrite the configuration files of all instances. The new versions of these files include any new entries found in the latest version of the model.

• Verify the SSH connectivity between hosts.

  Note:

  If you recently added new instances to the model or have yet to set the required passwordless SSH access to the hosts managing instances, either manually set the required passwordless SSH access for the instance administrator or use the ttGridAdmin gridSshConfig command before applying the latest version of the model. See Setting Passwordless SSH.

• Start new instances.

Apply all the changes made to the latest version of the model of the grid1 grid.

% ttGridAdmin modelApply
Creating new model version............................................OK
Exporting current model (version 1)...................................OK
Identifying any changed management instances..........................OK
Identifying any deleted objects.......................................OK
Verifying installations...............................................OK
Verifying instances...................................................OK
Creating new instances................................................OK
Updating grid state...................................................OK
Configuring instance authentication...................................OK
Pushing new configuration files to each instance......................OK
Making model version 1 current, version 2 writable....................OK
Checking ssh connectivity of new instances............................OK
Starting new management instance......................................OK
Configuring standby management instance...............................OK
Starting new data instances...........................................OK
ttGridAdmin modelApply complete

Given all the tasks you performed in the previous topics, the ttGridAdmin modelApply command performs the following operations:

1. Creates a copy of the installation files on every configured host:
2. Creates the instance home directory and files for the standby management instance and data instances on their associated hosts:
3. Makes the latest version of the model read-only and a creates a new writable model.
4. Verifies SSH connectivity to every configured host.
5. Starts the daemons of the standby management instance and data instances.
6. Configures the active and standby management instances.

For more information on the ttGridAdmin modelApply command, see Apply the Latest Version of the Model (modelApply) in Oracle TimesTen In-Memory Database Reference.