SAVESynchronously snapshot the dataset to disk.
| 语法 | SAVE |
| 分组 | server |
| 参数个数 | 1 |
| 起始版本 | 1.0.0 |
| 标志 | write, admin |
| 复杂度 | O(S) fan-out; O(N/S) copy-on-write freeze per shard |
| Redis 兼容性 | differs: SAVE is no longer synchronous-until-durable — it freezes a copy-on-write view and replies OK immediately, so 'SAVE returned, therefore the dump is safe to copy' no longer holds |