# Switch to readonly mode

The API runs in **readwrite** mode by default, holding a full SPACE GASS
license seat. If you only need to query results, switch to **readonly**
mode to release the seat — freeing it for the desktop application or
another API instance.

Readonly mode must be set **before** opening a job. If a job is already
open, you must close it first — the mode switch is queued until the job
closes.

## Switch to readonly, open, query, close

The snippet below switches to readonly, opens a sample project, queries
node reactions from a previous analysis, then closes the job. Because
the mode was set before opening, the API never acquires a SPACE GASS
license seat.

<CodeTabs>
```csharp title="C#"
using SpaceGassApi;
using SpaceGassApi.Models;

var client = SpaceGassApiClient.CreateClient("http://localhost:34560");

// Switch to readonly before opening — no SPACE GASS seat consumed
await client.Service.AccessMode.PostAsync(
    new AccessModeUpdate { AccessMode = AccessMode.ReadOnly });

try
{
    await client.Job.OpenSample.PostAsync(
        new OpenSampleRequest { FileName = "Portal Frame.SG" });

    // Query existing analysis results (read-only operations only)
    var reactions = await client.Job.Query.Analysis.Static.NodeReactions.GetAsync();

    foreach (var r in reactions!.Results!)
    {
        Console.WriteLine($"Node {r.Node}, LC {r.LoadCase}: Fy={r.Fy:F2} kN");
    }
}
finally
{
    await client.Job.Close.PostAsync();

    // Restore readwrite when finished
    await client.Service.AccessMode.PostAsync(
        new AccessModeUpdate { AccessMode = AccessMode.ReadWrite });
}
```

```python title="Python"
from space_gass_api import SpaceGassApiClient
import space_gass_api.models as models

client = SpaceGassApiClient.create_client("http://localhost:34560")

# Switch to readonly before opening — no SPACE GASS seat consumed
await client.service.access_mode.post(
    models.AccessModeUpdate(access_mode=models.AccessMode.ReadOnly))

try:
    await client.job.open_sample.post(
        models.OpenSampleRequest(file_name="Portal Frame.SG"))

    # Query existing analysis results (read-only operations only)
    reactions = await client.job.query.analysis.static.node_reactions.get()

    for r in reactions.results:
        print(f"Node {r.node}, LC {r.load_case}: Fy={r.fy:.2f} kN")
finally:
    await client.job.close.post()

    # Restore readwrite when finished
    await client.service.access_mode.post(
        models.AccessModeUpdate(access_mode=models.AccessMode.ReadWrite))
```

```bash title="curl"
# Switch to readonly
curl -X POST http://localhost:34560/api/v1/service/access-mode \
  -H "Content-Type: application/json" \
  -d '{"accessMode": "ReadOnly"}'

# Open a sample (read-only — no SPACE GASS seat consumed)
curl -X POST http://localhost:34560/api/v1/job/open-sample \
  -H "Content-Type: application/json" \
  -d '{"fileName": "Portal Frame.SG"}'

# Query reactions
curl http://localhost:34560/api/v1/job/query/analysis/static/node-reactions

# Close and restore readwrite
curl -X POST http://localhost:34560/api/v1/job/close
curl -X POST http://localhost:34560/api/v1/service/access-mode \
  -H "Content-Type: application/json" \
  -d '{"accessMode": "ReadWrite"}'
```
</CodeTabs>

### What if a job is already open?

If you call `POST /service/access-mode` with `"ReadOnly"` while a job is open,
the API returns **202 Accepted** — the transition is queued and commits
when the job closes. Close the job first if you need the mode to take
effect immediately.

If all license seats are in use when switching back to readwrite, the
API returns **409 Conflict** and stays in readonly.

### Check the current mode

Use `GET /service/access-mode` (the `accessMode` and `pendingAccessMode`
fields) to see the active mode and any pending transition.

## See also

- [Licensing](/licensing) — full explanation of readwrite and
  readonly modes
- [Concepts — The Active Job](/concepts#the-active-job)