Instances
The Instances tab displays all configured instances for your Oracle database service in a table, with per-instance details and actions including switchover, DR drills, and replica creation.
What instance topologies does Tessell support for Oracle?
Single instance
One instance in a given region and availability zone.
Multi-AZ (HA)
Two instances — one primary and one synchronous HA replica — in the same region (same or different AZ). A third observer node manages automatic failover. Both instances are always homogeneous (compute, storage, IOPS, parameters). All planned operations run in rolling mode to minimise downtime.
Disaster Recovery (DR)
One or more async replica instances added in the same or a different region. No automatic failover. DR-Drill scenario is supported. Can be added to both single-instance and Multi-AZ services.
Read Replica (RR)
An async replica opened in read-only mode. Requires an active Oracle Data Guard license. Use for read-only query offloading.
What columns appear in the Instances table?
Name
Auto-generated name: default-node-0 (primary), default-node-1 (HA replica), <name>-node-<n> (RR/DR).
Status
Current instance state (see table below).
Role
Primary, HA Replica (Automatic Failover), RR (Read Replica), or DR (Disaster Recovery). Shows the server name below the role.
Region/Zone
Cloud provider, region, and availability zone/set.
Parameter Profile
Parameter profile applied at provisioning.
Option Profile
Option profile applied at provisioning.
Compute
Compute shape with vCPU and memory details below.
Created
Date and time the instance was created.
Storage
Storage size; click See details for throughput, IOPS, and storage provider.
Connection Endpoint
Hostname; click See details for host, port, username, and service URL.
Instance status reference
UP
Instance is running and accepting connections.
Resize compute/storage, update parameter profile, delete (RR/DR only)
DOWN
Instance is down.
Raise a Tessell support ticket
STOPPED
Instance is completely stopped.
Start the service
CREATING
Provisioning in progress.
No actions
DELETING
Deletion in progress (RR/DR only).
No actions
REBUILDING
Compute or storage resize in progress.
No actions
REBUILD_FAILED
Resize did not complete.
All actions
PATCHING
Oracle patch being applied.
No actions
PATCH_FAILED
Patching failed.
All actions
UPDATING_PARAMETER_PROFILE
Parameter profile update in progress.
No actions
PARAMETER_PROFILE_UPDATE_FAILED
Parameter profile update failed.
All actions
How do I manually trigger a switchover to an HA replica?
Switchover promotes a replica (HA or DR) to become the new primary. Tessell automatically updates the service-level DNS hostname to point to the new primary, so applications transparently redirect without reconfiguration.
Note: Switching to an HA replica is graceful (no data loss); switching to a DR replica follows DR Drill rules (see below).
Steps to initiate a switchover
Click Switch over on the Instances tab.
In the Switch over to an instance window, select the target replica instance.
Optionally add comments.
Select the I understand the consequences checkbox.
Click Switch.
Monitor progress by clicking Submitting Request below the service name.
What is the difference between a DR Drill and an actual disaster recovery switchover?
When switching over to a DR instance, Tessell offers two paths:
DR Drill (Graceful)
Yes
Attempts a graceful switchover: all transactions committed, primary demoted cleanly, DR instance promoted with full data consistency. If graceful switchover is not possible, the operation fails. Used for compliance testing — switchback to original primary is possible after the drill.
Actual Disaster Recovery (Forceful)
No
Assumes a real disaster. DR instance is forcefully promoted to primary. Original primary is marked unrecoverable and brought down. Tessell automatically triggers a rebuild of the original primary. Switchback is possible after rebuild completes.
Feature comparison
Switchover type
Graceful
Forceful
Data consistency check
Yes
Skipped
Source primary status
Demoted cleanly
Brought down
Automatic rebuild of source
No (optional switchback)
Yes (required for future use)
Switchback possible
Yes (post-drill)
Yes (post-rebuild)
Use case
Testing / Compliance
Actual Disaster / Failover
How do I add a DR or Read Replica instance?
You must open bi-directional network communication between the primary and the DR/RR subnets:
Primary database port (e.g., 1521 for Oracle)
Port 1599
Applied at the subnet level (entire CIDR blocks), not VM level — NSG/security group rules at the VM level are managed by Tessell.
Availability Set placement behaviour
DR instance
Placed in a separate Availability Set from Primary and HA nodes. This ensures that when a DR switchover occurs, the new primary already has its own independent AS ready for its HA standby.
Read Replica
Placed in the same Availability Set as Primary and HA nodes. RR instances are never promoted to primary.
Steps to add a DR or Read Replica instance
Click Create Replica (top-right of the Instances tab).
Select Disaster Recovery or Read Only Replica.
Provide the following details:
Instance Name — alphanumeric characters only.
Region — target region.
Availability Zone — target AZ.
VPC — target VPC.
Private Subnet — target private subnet.
Advanced configuration — (optional) specify IOPS and Throughput. A different compute shape for DR/RR is also supported.
Click Add Instance.
Tessell automatically:
Submits the request to add the replica.
Creates the compute instance(s).
Prepares the primary database to accept the new replica.
Configures the replica with primary database information.
Sets up the Availability Machine for the new instance.
As an alternative, use the Code button to generate API calls in Shell, Python, Go, Java, JavaScript, or PowerShell.
Note: Using the ellipsis icon on individual instance rows, you can create, update, or delete private links for DR and RR nodes separately.
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