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

# Release Notes for mongosync 1.9

This page describes changes and new features introduced in MongoDB Mongosync 1.9.

## 1.9.0 Release

**November 13, 2024**

### Embedded Verifier

Starting in 1.9.0, `mongosync` includes an embedded verifier to confirm the successful sync of collections from the source cluster to the destination. The verifier is enabled by default for replica set migrations.

**Note:**

If you live upgrade from any version before 1.9.0, `mongosync` disables embedded verification.

To check verification status, see the `verification` field in the [/progress](https://www.mongodb.com/docs/mongosync/current/reference/api/progress.md#std-label-c2c-api-progress) response.

For details, see [Verify with Embedded Verifier.](https://www.mongodb.com/docs/mongosync/current/reference/verification/embedded.md#std-label-c2c-embedded-verifier)

### Other Notes

New Features:

- `mongosync` now supports migrating documents that have an empty timestamp values, such as Timestamp(0,0) for source clusters using MongoDB version 6.0 or later.

- Added a `stdin` disclaimer to the `mongosync` executable regarding verification. Users must to accept this disclaimer before `mongosync` can run.

- Added `--acceptDisclaimer` flag for users that have previously read the disclaimer to bypass it.

- Added a memory check in the `/start` endpoint for enabling verification. Verification requires 10 GB of base memory and 0.5 GB per 1 million documents.

Optimizations:

- Increased internal timeout to reduce the occurrence of timeout failures during initialization

## Minimum Supported Version

In 1.9.0, the minimum supported versions of MongoDB are 6.0.17 and 7.0.13.

For best performance, upgrade your source and destination clusters to the most recent MongoDB Server patch release prior to migration. For more information, see [Upgrade to the Latest Self-Managed Patch Release of MongoDB.](https://www.mongodb.com/docs/manual/tutorial/upgrade-revision.md#std-label-upgrade-to-latest-revision)