# Operations

> Track active merges, historical merge performance, mutations, part moves, and the part-event timeline for all MergeTree tables.

| | |
|---|---|
| **Routes** | `/merges`, `/merge-performance`, `/mutations`, `/moves`, `/part-log` |
| **Feature id** | `operations` |
| **Default access** | `public` |
| **Requires auth** | No (set `CHM_FEATURE_OPERATIONS_ACCESS=authenticated` to gate) |
| **System tables** | `system.merges`, `system.mutations`, `system.moves`, `system.part_log` |
| **ClickHouse grants** | `SELECT` on the system tables above; `KILL MUTATION` for the kill-mutation action |

## What it does

Operations covers the background work MergeTree engines do continuously:

- **Merges** — which parts are being merged right now, progress percentage, estimated completion, rows and bytes processed.
- **Merge performance** — historical trends from the part log: merge size, duration, and throughput over time.
- **Mutations** — `ALTER TABLE ... UPDATE/DELETE` operations: how many parts remain, any failures.
- **Moves** — parts currently being moved between disks or volumes due to TTL or storage policy rules.
- **Part log** — the full part-event history: part creation, merges, mutations, downloads from replicas, and removals.

All pages are read-only except the kill-mutation action on `/mutations`.

## Pages

| Page | Route | What it shows | System tables |
|---|---|---|---|
| Merges | `/merges` | Active merge list: table, progress %, elapsed, rows/bytes merged, estimated finish | `system.merges` |
| Merge Performance | `/merge-performance` | Historical merge stats from the part log: size buckets, duration trends | `system.part_log` |
| Mutations | `/mutations` | Pending and completed mutations: parts\_to\_do, is\_done, failure reason; kill action | `system.mutations` |
| Moves | `/moves` | In-progress part moves: source/target disk, part name, size, elapsed | `system.moves` |
| Part Log | `/part-log` | Part lifecycle events: NewPart, MergedPart, MutatedPart, DownloadedPart, RemovedPart | `system.part_log` |

## Permissions & access

All sub-routes share the `operations` feature id:

```bash
## Gate to authenticated users
CHM_FEATURE_OPERATIONS_ACCESS=authenticated

## Disable entirely
CHM_FEATURE_OPERATIONS_ENABLED=false
## or
CHM_DISABLED_FEATURES=operations
```

```toml
## CHM_CONFIG_FILE (TOML)
[features.operations]
access = "authenticated"
```

## Configuration

No feature-specific configuration. Global settings apply:

```bash
CLICKHOUSE_MAX_EXECUTION_TIME=60
```

## Notes & limitations

- **`system.part_log`** — requires `<part_log>` to be enabled in the ClickHouse server config. It is disabled by default on some distributions. If absent, `/merge-performance` and `/part-log` show a table-not-found notice.
- **`system.moves`** — only populated when a TTL or storage policy move is actively in progress. The table is empty between moves; this is normal.
- **Kill mutation** — the kill-mutation button on `/mutations` issues `KILL MUTATION`. The ClickHouse user must have `ALTER TABLE` privilege (or specifically `KILL MUTATION`). Without it the action returns an error.
- **Merge progress** — `system.merges` shows only active merges. Completed merges appear in `system.part_log` with event type `MergedPart`.
- The `/merges` route is also the entry point for the Operations section in the nav (feature id `operations`).

## Related

- [Tables](/features/tables)
- [Queries](/features/queries)
- [Authentication](/authentication)
- [Settings reference](/settings)