> For the complete MongoDB documentation index, see www.mongodb.com/docs/llms.txt

# Reverse Sync Direction

To reverse the direction of a sync operation, use the following procedure to [commit your sync](https://www.mongodb.com/docs/mongosync/current/reference/cutover-process.md#std-label-c2c-cutover-process) and call the `reverse` endpoint.

If you want to keep your source cluster updated with new writes from your destination cluster post-cutover, you can use `reverse`. For more details, see [Mid-sync Considerations.](https://www.mongodb.com/docs/mongosync/current/reference/mongosync-behavior.md#std-label-mongosync-considerations)

## Before You Begin

Before you can reverse your sync direction, you must configure `mongosync` and use the [`start`](https://www.mongodb.com/docs/mongosync/current/reference/api/start.md#std-label-c2c-api-start) endpoint to set the `reversible` option to `true`.

**Warning:**

[Unique indexes](https://www.mongodb.com/docs/manual/core/index-unique.md#std-label-index-type-unique) on the source cluster must not use the legacy format.

To validate that collection indexes on the source cluster use the proper formatting, see [Validate Unique Indexes.](https://www.mongodb.com/docs/mongosync/current/reference/api/reverse.md#std-label-c2c-validate-unique-index)

For more information on limitations and requirements of reversing sync, see [`reverse`.](https://www.mongodb.com/docs/mongosync/current/reference/api/reverse.md#std-label-c2c-api-reverse)

**Important:**

If you are migrating from a pre-6.0 source cluster, you cannot reverse sync.

## Steps

Use these steps to reverse the direction of your sync:

1. Finalize your sync.

   Follow the [Finalize Cutover Process](https://www.mongodb.com/docs/mongosync/current/reference/cutover-process.md#std-label-c2c-cutover-process) tutorial to finalize your data migration.

   IMPORTANT: `mongosync` does not support [Filtered Sync](https://www.mongodb.com/docs/mongosync/current/reference/collection-level-filtering.md#std-label-c2c-filtered-sync) during the reverse sync process.

2. Call the `reverse` endpoint.

   Call the `reverse` endpoint to reverse the direction of your sync operation. Your original source cluster becomes your new destination cluster and your original destination cluster becomes your new source cluster.

   `mongosync` replicates all writes that you performed on your new source cluster after you unblocked writes (during step 4 of the [Finalize Cutover Process](https://www.mongodb.com/docs/mongosync/current/reference/cutover-process.md#std-label-c2c-cutover-process)) to the new destination cluster.

3. Finalize your reverse sync.

   Follow the [Finalize Cutover Process](https://www.mongodb.com/docs/mongosync/current/reference/cutover-process.md#std-label-c2c-cutover-process) tutorial to enable write blocking and finalize your reverse data migration.

   **Note:**

   Since the source and destination clusters swap after calling the `reverse` endpoint, "source" refers to the old destination cluster and the "destination" refers to the old source cluster.