> ## Documentation Index
> Fetch the complete documentation index at: https://docs.tandemn.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Replica operations

> Add, kill, and hot-swap Tandemn replica clusters.

Replica commands operate on running jobs that use chunked execution. New replicas join the same Redis chunk queue, and killed replicas have in-flight chunks reclaimed and returned to pending.

## Add replicas

```bash theme={null}
tandemn add <job_id> 2
tandemn add <job_id> 3 --gpu L40S --tp 4
```

The first command adds two replicas that inherit the job's current GPU configuration. The second command adds three L40S replicas, creating a heterogeneous fleet.

| Argument or flag | Description                                                 |
| ---------------- | ----------------------------------------------------------- |
| `job_id`         | Running job to scale.                                       |
| `N`              | Number of replicas to add.                                  |
| `--gpu <type>`   | Optional GPU type override for the new replicas.            |
| `--tp N`         | Optional tensor parallelism override.                       |
| `--pp N`         | Optional pipeline parallelism override.                     |
| `--on-demand`    | Launch new replicas on on-demand instances instead of spot. |

## Kill replicas

```bash theme={null}
tandemn kill <job_id> --replica <rid>
tandemn kill <job_id> --replica r0 --replica r1
```

Use `tandemn kill` to terminate specific replicas. Any chunk leased by a killed replica is reclaimed and returned to the queue.

| Flag              | Description                                                    |
| ----------------- | -------------------------------------------------------------- |
| `--replica <rid>` | Replica ID to kill. Repeat the flag to kill multiple replicas. |

## Hot-swap replicas

```bash theme={null}
tandemn swap <job_id> --gpu A100 --tp 4 --replicas 2
tandemn swap <job_id> --gpu L40S --tp 1 --ready-threshold 2 --on-demand
```

Hot-swap replaces all replicas with a new GPU configuration mid-job. Tandemn launches the replacement replicas first, waits for them to begin processing, and then tears down the old replicas.

| Flag                  | Description                                                                |
| --------------------- | -------------------------------------------------------------------------- |
| `--gpu <type>`        | GPU type for the replacement fleet.                                        |
| `--tp N`              | Tensor parallelism for replacement replicas.                               |
| `--pp N`              | Pipeline parallelism for replacement replicas.                             |
| `--replicas N`        | Number of replacement replicas.                                            |
| `--ready-threshold N` | Number of new replicas that must be ready before old replicas are removed. |
| `--on-demand`         | Use on-demand instances for the replacement fleet.                         |

## Operational notes

* Replica operations require Redis-backed chunk coordination.
* Killed replicas do not lose completed chunks.
* Hot-swap is designed to avoid dropped chunks by keeping the shared queue intact.