> For the complete documentation index, see [llms.txt](https://docs.tessell.com/tessell/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tessell.com/tessell/database-engines/tessell-for-oracle/db-services/my-services/database-service-home-page/instances.md). # 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? | Instance type | Description | | -------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | **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? | Column | Description | | ----------------------- | ----------------------------------------------------------------------------------------------------------------------------- | | **Name** | Auto-generated name: `default-node-0` (primary), `default-node-1` (HA replica), `-node-` (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 | Status | Description | Actions allowed | | -------------------------------------- | ---------------------------------------------- | --------------------------------------------------------------------- | | **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 1. Click **Switch over** on the Instances tab. 2. In the **Switch over to an instance** window, select the target replica instance. 3. Optionally add comments. 4. Select the **I understand the consequences** checkbox. 5. Click **Switch**. 6. 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: | Mode | DR Drill option selected | Behaviour | | --------------------------------------- | ------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | **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 | Feature | DR Drill Enabled | DR Drill Disabled (Disaster Mode) | | --------------------------- | ------------------------ | --------------------------------- | | 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 | Replica type | Placement | | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | **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 1. Click **Create Replica** (top-right of the Instances tab). 2. Select **Disaster Recovery** or **Read Only Replica**. 3. 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. 4. Click **Add Instance**. Tessell automatically: 1. Submits the request to add the replica. 2. Creates the compute instance(s). 3. Prepares the primary database to accept the new replica. 4. Configures the replica with primary database information. 5. 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. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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