Before you migrate your service instances from Oracle Cloud Infrastructure Classic to Oracle Cloud Infrastructure, understand how the migration affects your existing instances, identify the necessary compute shapes, and create the network to support your migrated service instances.
About Downtime Requirements
The migration process does not affect the availability of your existing Oracle Java Cloud Service instance in Oracle Cloud Infrastructure Classic. This instance continues to run and can serve client requests during this process.
You can discover and export the configuration from your source Oracle WebLogic Server domain while it is running. The migration tool does not modify your domain or significantly affect its performance.
After a service instance is migrated successfully, clients can be rerouted to the new instance in Oracle Cloud Infrastructure.
Select Oracle Cloud Infrastructure Shapes
Identify the compute shapes that provide similar IaaS resources in Oracle Cloud Infrastructure to the shapes that you're currently using for your service instances in Oracle Cloud Infrastructure Classic.
A compute shape defines the IaaS resources, such as OCPUs and memory, that are available to a specific node in a service instance. Oracle Cloud Infrastructure and Oracle Cloud Infrastructure Classic each has its own set of standard compute shapes. See:
- About Shapes in Using Oracle Cloud Infrastructure Compute Classic
- Compute Shapes in the Oracle Cloud Infrastructure documentation
To ensure that a migrated service instance has the same performance characteristics as the original instance, and can support an equivalent workload, choose Oracle Cloud Infrastructure shapes that most closely map to the Oracle Cloud Infrastructure Classic shapes that you specified when you created the instance.
You must also confirm that the chosen shapes are available in your Oracle Cloud tenancy. Oracle configures shape limits for an Oracle Cloud Infrastructure region, or for a specific availability domain within a region. You can use the console to view the current shape limits for your tenancy, and to request a limit increase if necessary. See Service Limits in the Oracle Cloud Infrastructure documentation.
If you use the Oracle Cloud Infrastructure Classic Java Migration Tool to create the target service instance, the tool automatically selects a corresponding shape in Oracle Cloud Infrastructure.
Note that unlike nodes in Oracle Cloud Infrastructure Classic, you cannot change the shape of an existing node (scale up or down) in Oracle Cloud Infrastructure. However, you can add storage to an existing node if necessary.
Design the Oracle Cloud Infrastructure Network
Before you migrate your service instances from Oracle Cloud Infrastructure Classic to Oracle Cloud Infrastructure, you must design and implement a virtual cloud network (VCN) to support your migrated service instances.
You can create new Oracle Cloud Infrastructure compartments, VCNs, and subnets for your service instances, or you can use existing ones. See these topics in the Oracle Cloud Infrastructure documentation:
Consider the following guidelines when you create or select a network for your service instances:
- If instances communicate using the default shared network in Oracle Cloud Infrastructure Classic, then use a single subnet for these instances.
- If instances are on separate IP networks in Oracle Cloud Infrastructure Classic, then use separate subnets for these instances.
- A VCN should have an address range that includes all of the IP networks in Oracle Cloud Infrastructure Classic that need to communicate. Alternatively, configure peering between multiple VCNs.
- A subnet should have at least the same number of addresses as the corresponding IP network in Oracle Cloud Infrastructure Classic.
- If an instance was created in Oracle Cloud Infrastructure Classic without public IP addresses, then use a private subnet for this instance.
- If custom access rules were created for an instance in Oracle Cloud Infrastructure Classic to control communication to or from the instance, then create a security list in Oracle Cloud Infrastructure and assign the security list to the appropriate subnets. To use custom security lists, you must assign the instance to a custom subnet, and not the default subnet.
Oracle Cloud Infrastructure Classic Java Migration Tool creates a bastion compute instance in Oracle Cloud Infrastructure in order for the migration controller (Control-S) compute instance to access your target service instance. After updating the target service instance, the tool deletes the temporary bastion compute instance.
Before you create service instances in Oracle Cloud Infrastructure that use your new network resources, you must create policies that grant your service access to these resources. See Prerequisites for Oracle Platform Services in the Oracle Cloud Infrastructure documentation.
Configure Security Rules for the Network
If your instance communicates with other resources in Oracle Cloud or on the Internet, create or update the security lists for your target Oracle Cloud Infrastructure network.
A security list is assigned to subnets within your virtual cloud network (VCN). It includes ingress and egress rules that specify the types of traffic allowed in and out of the instances within the subnet. You can update an existing security list, or create a new one and assign it to a subnet.
You might need to create security rules if your Oracle Java Cloud Service instance communicates with external resources, including these Oracle WebLogic Server resources:
- JavaMail Session
- Foreign Java Naming and Directory Interface (JNDI) Provider
- Foreign Java Message Service (JMS) Server
- Messaging Bridge
- WebLogic Diagnostic Framework (WLDF) REST Action
See Security Lists in the Oracle Cloud Infrastructure documentation.