Overview of Oracle Cloud Migrations

The Oracle Cloud Migrations service provides an end-to-end comprehensive self-service experience for migrating existing VMware virtual machine-based workloads from on-premises to Oracle Cloud Infrastructure (OCI).

Oracle Cloud Migrations enables you to identify virtual-machine workloads hosted in an environment external to OCI, plan migrations, and automate migration workflows.

The Oracle Cloud Migrations service enables you to perform the following tasks:

  • Automatically discover virtual machines external to Oracle Cloud Infrastructure.
  • Organize virtual machines for migration.
  • Replicate the virtual machine data to OCI.
  • Plan the redeployment of virtual machines.
  • Reconfigure virtual machines to launch successfully as OCI compute instances automatically.
  • Launch virtual machines as OCI compute instances using replicated data.

Oracle Cloud Migrations Workflow

OCM workflow

The workflow is based on the following five modules that enable migration:

  • A virtual appliance is deployed in your on-premises environment.
  • The appliance launches two plugins - discovery and replication.
  • The discovery plugin searches for VMware virtual machines in the source environment using environment-specific connectors.
  • The replication plugin manages the replication of source assets snapshots from the source environment to OCI.
  • The inventory module retrieves metadata information that tracks the virtual machine's physical and runtime properties, such as operating system, hardware, and resource utilization. The module then stores them in the inventory service.
  • The inventory module is used to store information about virtual machines discovered in the on-premises environment that can be migrated. These machines are added to inventory by using API and importing the CSV file, or by running automated discovery in the external environment.
Assessment and Planning
  • Oracle Cloud Migrations provides ongoing inventory analysis that contains statistics, summaries, and histograms about the virtual machines in your inventory.
  • A virtual machine contains metadata and metrics along with their history and how they are discovered or imported. Metadata history is tracked so that you can monitor a virtual machine's evolution over the course of their long-running migration. Hence, Oracle Cloud Migrations can highlight any changes that might require revisiting the migration plan.
  • A migration project is created that contains the migration plans for replicating the virtual machines.
  • A migration plan can group interrelated and dependent virtual machines that can be migrated together.
  • VMware virtual machines reference a replication policy that describes how the machines are migrated into OCI.
  • Replication plugin manages the replication of external assets snapshots. Oracle Cloud Migrations determines and manages full-image or incremental virtual-machine snapshots. For information about replication, see Understanding VM Replication.
  • Within a project, you create migration plans. A migration plan is a mapping of VMware virtual machines to target resource types in OCI. A migration plan provides the context to launch virtual machines, including compartment, subnets, and launch dependencies.
  • The virtual machines are replicated on OCI instances.
  • You can mark the project as complete. After a project is marked complete, Oracle Cloud Migrations decouples the production environment from the migration workflow and archives migrated inventory.
Using Oracle Cloud Migrations, you can accelerate your journey to Oracle Cloud by automating the asset discovery, migration planning, and replication processes through the Oracle Cloud Console, REST API, and CLI. See Accessing Oracle Cloud Migrations. To get started with Oracle Cloud Migrations, see Getting Started with Oracle Cloud Migrations.

Oracle Cloud Migrations Terminologies

Review the following terms to understand the Oracle Cloud Migrations service.

agent dependency

Third-party libraries that are required for migration tasks. To comply with licensing terms, you must obtain these libraries separately and make them available to the remote agent appliance.


The Oracle Cloud Migrations service works with multiple types of assets including virtual machines and their associated data disks. Assets are categorized depending on the stage of the migration workflow. Refer to the following asset types:

  • external asset: The external assets are hosted in an external environment outside Oracle Cloud Infrastructure (OCI). For example, a VMware vSphere environment that is located on-premises.
  • inventory asset: A representation of a resource that exists outside of OCI. These resources contain metadata, metrics, history, and how the physical or virtual entities are discovered and imported. Assets can be added to inventory by running discovery in the source environment, CSV import, or using the API.
  • migration asset: A migration asset is defined by an inventory asset and an associated replication location for a migration project. It can only belong to a single migration project. Migration assets can be replicated manually or scheduled as part of a migration project.
  • target asset: An asset in a migration plan that represents the deployment configuration, which launches an OCI native resource, and with that completing the migration of an external asset.
asset source
The asset source represents the connectivity information for a source environment that you define. An asset source can be an on-premises environment or another cloud environment, which is the source of the assets to be migrated to OCI.
discovery schedule

Defines the frequency at which a work request is created to refresh an asset source against a source environment. The work request adds new inventory assets and refreshes the metadata for existing inventory assets.

external asset discovery

A process to ingest and store collected external asset metadata to inventory.

external environment

An on-premises or cloud environment from which external assets are migrated to OCI.

hydration agent
A hydration agent is a temporary compute instance that is launched in your tenancy during the migration. A hydration agent reads and writes replicated source data from object storage to target boot or block volumes.

A collection of assets and associated metadata that represent external assets that can be selected for migration to OCI.

migration project

A collection of migration assets and migration plans. The project enables scheduled replication for all associated migration assets. A migration project can have multiple migration plans.

migration plan

Provides a mapping between selected Migration Assets and a target environment. A plan allows you to configure each target asset in the target environment. Also, a plan analyzes each target asset configuration for compatibility of migration. Each migration plan includes a migration strategy and cost estimate based on the strategy.

remote agent appliance

A prebuilt virtual machine provided by Oracle that is deployed in an external environment to perform discovery of external assets and replication of data. The appliance includes several plugins, which perform service-specific operations and facilitate communication with OCI. The following are the plugin descriptions:

  • Discovery: The discovery plugin collects metadata about external assets and creates representative assets in inventory.
  • Replication: The replication plugin manages the copy and transfer of virtual disks to OCI Object Storage.
  • AgentHealthMonitoring: The AgentHealthMonitoring plugin monitors core processes running on the remote agent appliance, and pushes periodic status messages to OCI.
replication location

A user-specified compartment and an object storage bucket that is used as the destination for replicated data.

replication schedule

A user-specified schedule for replicating external asset data of each migration asset in a migration project.

source environment

The OCI representation of an external environment. All connections between external environments and OCI are established by registering remote agent appliances to the source environment. An environment can include multiple remote agent appliance and any associated agent dependencies.

Tenancy Resources Used in Migration

During the migration process, Oracle Cloud Migrations creates temporary resources in your tenancy. Although there is no cost for using the service, temporary resources are billed at the normal rate for the tenancy.

You can set a limit to the resources and to know about the limit that you can set, see Service Limits. These limits can be increased for you automatically based on your Oracle Cloud Infrastructure resource usage and account standing.


Ensure that you don't modify the following temporary resources. Modifying temporary resources created by Oracle Cloud Migrations might cause pending operations to fail.
  • Compute: Oracle Cloud Migrations launches compute instances to run hydration agents during data replication. The hydration agents are pooled together based on the replication location. To load balance the replication process based on the object pool, the hydration agents start automatically. These agents are automatically terminated after they are idle and no pending replication jobs exist. To familiarize yourself with the compute services, see Overview of the compute service.
  • Object Storage: During the replication workflow, the volume snapshots of your VMs are stored in the Object Storage. The snapshot data is deleted from object storage after hydration agents write the data to a block volume. To familiarize yourself with object storage, see Overview of Object Storage.
  • Virtual Cloud Network (VCN): During the replication workflow, a temporary VCN is created to provide hydration agents with connectivity to object storage. The VCN is stopped after all hydration agents are no longer active. To familiarize yourself with VCN, see Networking Overview.
  • Block Storage: A set of block volumes exists in your tenancy for the entire lifespan of a migration asset. A golden volume is created for each boot and data volume that is attached to the source virtual machine. The golden volume is kept in synchronization with snapshots created in the source environment. As part of each replication update, a new set of volumes is created and used for launching compute instances on OCI. To familiarize yourself with Block Volume, see Overview of Block Volume.

Accessing Oracle Cloud Migrations

You can access Oracle Cloud Migrations by using the Console (a browser-based interface), Oracle Cloud Infrastructure (OCI) command line interface (CLI), or the REST API. Instructions for the Console, CLI, and API are included in topics throughout this guide.

You can access Oracle Cloud Migrations using the following methods.

If you get a permission or authorization error, contact your administrator, and check the type of access that you are granted.

Regions and Availability Domains

Oracle Cloud Migrations is hosted in all Oracle Cloud Infrastructure commercial regions.

Ensure that you configure Oracle Cloud Migrations in each region that you migrate virtual-machines workloads to. If you're migrating VMs to multiple OCI regions, each region must be configured separately.

For OCI, see About Regions and Availability Domains for the list of available regions. Also, the associated locations, region identifiers, region keys, and availability domains are specified.

Limits and Quotas in Oracle Cloud Migrations

A service limit is the quota or allowance set on the resources that you use when accessing the migration services.

The following are the resources and the Oracle Cloud Migrations service limits for your region:

Resource Group Resource Name/Description Limit Name Default Service Limit Default Pay-as-you-go
OCB Discovery Asset Source Count asset-source-count 20 10
Discovery Schedule Count discovery-schedule-count 5 5
OCB Inventory Number of assets that can be created in inventory asset-count 5000 1000
Oracle Cloud Migrations Number of migration projects migrations-count 20 10
Number of migration plans migration-plans-count 50 25
Number of assets in migrations migration-assets-count 1000 100
Number of target assets in migrations migration-targetassets-count 1000 100
Number of replication schedules replication-schedule-count 10 5
Maximum Environment Count environment-count 10 5
Maximum Agent Count agent-count 20 10
Maximum Agent Dependency Count agent-dependency-count 20 10

To check the Oracle Cloud Migrations service limits, follow the given steps:

  1. From the Console, open the navigation menu, and click Governance & Administration.
  2. Under Governance, click Limits, Quotas, and Usage.
  3. Filter on the following values to view the resources and their limits:
    • Service: OCB Discovery, OCB Inventory, Oracle Cloud Migrations
    • Scope: <your region>
    • Compartment: <your-tenancy-namespace > (root)
  4. To increase the default service limits for any of the resources, click the request a service limit increase link.

    Only administrators can increase the service limit.

    For more information, see Service Limits.