Before it starts consuming the replication stream, Materialize takes a snapshot
of the relevant tables. Until this snapshot is complete, Materialize won't have
the same view of your data as your MySQL database.

In this step, you'll first verify that the source is running and then check the
status of the snapshotting process.

1. Back in the SQL client connected to Materialize, use the
   [`mz_source_statuses`](/sql/system-catalog/mz_internal/#mz_source_statuses)
   table to check the overall status of your source:

    ```mzsql
    WITH
      source_ids AS
      (SELECT id FROM mz_sources WHERE name = 'mz_source')
    SELECT *
    FROM
      mz_internal.mz_source_statuses
        JOIN
          (
            SELECT referenced_object_id
            FROM mz_internal.mz_object_dependencies
            WHERE
              object_id IN (SELECT id FROM source_ids)
            UNION SELECT id FROM source_ids
          )
          AS sources
        ON mz_source_statuses.id = sources.referenced_object_id;
    ```

    For each `subsource`, make sure the `status` is `running`. If you see
    `stalled` or `failed`, there's likely a configuration issue for you to fix.
    Check the `error` field for details and fix the issue before moving on.
    Also, if the `status` of any subsource is `starting` for more than a few
    minutes, [contact our team](/support/).

2. Once the source is running, use the [`mz_source_statistics`](/sql/system-catalog/mz_internal/#mz_source_statistics)
   table to check the status of the initial snapshot:

    ```mzsql
    WITH
      source_ids AS
      (SELECT id FROM mz_sources WHERE name = 'mz_source')
    SELECT sources.referenced_object_id AS id, mz_sources.name, snapshot_committed
    FROM
      mz_internal.mz_source_statistics
        JOIN
          (
            SELECT object_id, referenced_object_id
            FROM mz_internal.mz_object_dependencies
            WHERE
              object_id IN (SELECT id FROM source_ids)
            UNION SELECT id, id FROM source_ids
          )
          AS sources
        ON mz_source_statistics.id = sources.referenced_object_id
        JOIN mz_sources ON mz_sources.id = sources.referenced_object_id;
    ```
    <p></p>

    ```nofmt
    object_id | snapshot_committed
    ----------|------------------
     u144     | t
    (1 row)
    ```

    Once `snapshot_commited` is `t`, move on to the next step. Snapshotting can
    take between a few minutes to several hours, depending on the size of your
    dataset and the size of the cluster the source is running in.