HVA SQL Server to Binary Log Reader Migration FAQs

Binary Log Reader (BLR) is a proprietary Fivetran-developed incremental sync method that reads changes directly from SQL Server transaction logs. For more information, see our Binary Log Reader documentation.

We are ending support for the HVA SQL Server connector. It will be replaced by our SQL Server connector, which uses the Binary Log Reader incremental sync method.

Binary Log Reader provides a simpler user experience. Compared to the HVA SQL Server connector, Binary Log Reader has a smaller footprint on your source, is simpler to install and configure, and supports all the features available with HVA SQL Server. It also performs most transaction log processing in the Fivetran environment, reducing the processing load on your source host.

Binary Log Reader uses SQL Server Common Language Runtime (CLR) integration to run the Fivetran Binary Log Reader DLL on the SQL Server host. The DLL reads the SQL Server transaction logs and sends the relevant log records to Fivetran for processing.

Unlike the High-Volume Agent (HVA), which runs continuously, the Binary Log Reader DLL uses source resources only while a connection is syncing. A single Binary Log Reader installation on a SQL Server host can also support multiple SQL Server connections across multiple databases.

• September 1, 2026: Migration for HVA SQL Server connections becomes available in your Fivetran dashboard.
• December 1, 2026: End of Availability (EoA). You can no longer create new HVA SQL Server connections or resume paused connections. However, existing HVA SQL Server connections will continue to run. Fivetran Support will continue to address breaking issues and critical security vulnerabilities, but will no longer deliver feature enhancements for HVA SQL Server.
• March 1, 2027: End of Life (EoL). Any HVA SQL Server connections that have not been migrated will stop syncing at the end of this day.

Fivetran evaluates your HVA SQL Server connection configuration and replication state to determine whether the connection is eligible for migration. If a readiness test fails, Fivetran displays the issue and the steps required to resolve it.

When all readiness tests pass, the connection is migrated in place. The migration preserves the connection name, supported configuration, and transaction log position, and does not require a historical re-sync.

After migration, the connection uses Binary Log Reader as its incremental sync method and continues syncing to the same destination schema at the same sync frequency.

The migration to Binary Log Reader involves the following steps:

1. Check the migration guide

   • Open the Status tab on the connection details page
   • Click the View migration guide button in the blue banner

2. Complete prerequisites

   • Download the Binary Log Reader DLL
   • Download the PowerShell script
   • Run the PowerShell script
   • Complete the Windows Authentication setup (if applicable).

3. Validate eligibility

   • Click the "Test setup" button
   • If any tests fail, follow the instructions to fix them.

4. Migrate the connector

   • Click the Migrate button

For detailed step-by-step instructions, see our quickstart guide for HVA SQL Server migration.

No. The migration updates your existing connection to use Binary Log Reader.

Besides pausing your connection for a few seconds, migration does not require downtime. The connection is paused when you click the Migrate button and resumes once the migration is completed successfully.

The actual migration takes a few seconds, but the setup tests that determine whether a connector is eligible may take 1 to 3 minutes.

Yes. You can create a new Binary Log Reader connection, validate it, and then proceed with migrating your existing connection. For more information on creating a new connection with Binary Log Reader, see our setup guide.

No. Existing sync configuration (such as history mode or soft deletes) remains unchanged after migration.

No. Migration only changes the incremental sync method and does not impact the Monthly Active Rows (MAR) usage.

Open the Status tab on the connection details page.

If the connection is not eligible, a warning message lists the pre-migration requirements and any failed eligibility tests, along with exact remediation steps. After your connection meets the prerequisites and you run a sync, the warning automatically disappears.

No. Your connection's log position, along with all other relevant state, is recorded and copied over during the migration.

Yes. Migration requires a supported SQL Server version (2016-2025).

To set up the Binary Log Reader, you must have a SQL Server account with sysadmin privileges.

To read from online transaction logs using the Binary Log Reader method, you require the following permissions:

To easily grant all necessary permissions for your chosen configuration, run the installation script, or follow the instructions.

Your connection's Status tab lists the prerequisites and remediation steps specific to your environment. For step-by-step instructions, see our quickstart guide for HVA migration.

The Binary Log Reader installation script configures your SQL Server environment with the objects and permissions required to use Binary Log Reader.

For online transaction logs, the script enables SQL Server Common Language Runtime (CLR) integration, configures the Binary Log Reader DLL, creates the required stored procedures, and grants the Fivetran database user the permissions required to run Binary Log Reader.

For backup transaction logs, the script can be run in Backup Log mode, which does not require CLR integration or installation of the Binary Log Reader DLL.

The script requires a SQL Server account with sysadmin privileges during setup. The Fivetran database user used for ongoing syncs can use the minimal permissions required for replication.

Binary Log Reader installs only a small number of Fivetran stored procedures. These include the procedure used to read the SQL Server transaction log, a procedure used for diagnostic purposes, and, when applicable, procedures used for TDE certificate handling.

The exact procedures installed depend on your Binary Log Reader configuration.

No. The Binary Log Reader DLL uses read-only operations to capture binary data from the SQL Server transaction log.

Fivetran signs the Binary Log Reader DLL to verify its authenticity. During installation, the script verifies the DLL and configures SQL Server to trust the assembly. For SQL Server 2017 and later, the script also registers the assembly as a trusted assembly using its SHA2-512 hash.

The Binary Log Reader DLL has dependencies on Microsoft .NET Framework, SQL Server, and Windows APIs.

Yes. Binary Log Reader requires CLR integration when reading directly from online transaction logs.

If you configure Binary Log Reader to read from backup transaction logs, CLR integration and the Binary Log Reader DLL are not required.

Binary Log Reader does not send every transaction log record to Fivetran. The DLL filters out operations that are not relevant to replication before sending log records to Fivetran.

However, this filtering is not based on the tables selected in your Fivetran connection. Relevant log records for both selected and unselected tables may be sent to Fivetran. After Fivetran parses the table information, records for tables that are not included in your connection configuration are discarded.

Binary Log Reader reads SQL Server transaction log files using a DLL that runs within SQL Server through CLR integration.

SQL Server restricts direct access to transaction log files. The Binary Log Reader DLL uses the Windows ReadFile API to read these files. SQL Server considers file access from a CLR assembly to be an unsafe operation, which is why the CLR assembly requires UNSAFE permission.

No. The Fivetran database user used for ongoing syncs does not receive the UNSAFE ASSEMBLY permission.

The installation script grants UNSAFE ASSEMBLY to the login associated with the Binary Log Reader CLR assembly. The Fivetran database user receives the server-, database-, and stored-procedure permissions required to perform replication.

Yes. Binary Log Reader supports all data types supported by HVA SQL Server. It also supports the HIERARCHYID data type, which HVA SQL Server does not support.

DDL operations are parsed from the logs and, when possible, incorporated into the connection's schema model. Binary Log Reader can automatically detect and process tables and columns that are added or dropped.

Ensure all tables are syncing as expected and monitor your connection for errors or warnings over the next 24 to 48 hours.

Migration will not resync any tables. If tables begin to erroneously resync, contact our support team.

If you see a data integrity issue after migration, re-sync the affected tables. If the issue persists after re-sync, contact our support team.

If your connection is not eligible for migration, review the warning in the migration section of the Status tab to identify the issue. The warning lists missing prerequisites, permissions, or unsupported configuration, along with steps to resolve them. After resolving the issue, run a sync to re-check eligibility.

Contact our support team with a screenshot of the connection status and the eligibility failure messages. The eligibility warning contains instructions, context, and the SQL/steps to run. If applicable, include any DBA output that shows the nature of your problem in more detail. Fivetran can validate or help with staging tests.

Exceptions are possible, but they are evaluated on a case-by-case basis. Contact our support team to submit an exception request with justification and environment details. Fivetran reviews exception requests and approves them only with valid justification.

If your database is managed by a third party, coordinate with the vendor to enable the migration prerequisites (PDB service name, wallet access, required grants, ASM staging, etc.). If the vendor blocks migration, contact our support team and include vendor’s contact or justification; Fivetran evaluates exceptions on a case-by-case basis.

Security concerns when installing new software on a database host are common. Fivetran provides guidance and secure configuration options for environments with strict security requirements. If security policies prevent a required privilege, contact our support team including the specific security requirement so we can propose a locked-down permission pattern or evaluate an exception.

Contact our support team and we will be happy to help. In rare cases, we may roll the connector back to the HVA service while we work on improving the Binary Log Reader to accommodate your situation.