What causes Fabric Warehouse Error 24556?

Two or more concurrent pipeline runs or queries attempted to UPDATE, DELETE, MERGE, or TRUNCATE the same warehouse table at the same time. Long-running transactions holding snapshot versions overlap with other write transactions on the same table. Uncoordinated parallel pipeline executions targeting the same destination table without write-ordering controls. Retry logic in a pipeline triggered a second write attempt while the original transaction was still in progress

How do I fix Fabric Warehouse Error 24556?

Step 1: Identify the conflicting transactions by reviewing the Fabric Warehouse query activity logs to find concurrent write operations targeting the same table around the time of the error.. Step 2: Redesign parallel pipelines to serialize writes to shared tables using pipeline dependencies, triggers, or staging tables to prevent simultaneous modifications.. Step 3: For MERGE or UPSERT patterns, consider using a staging table approach where data is first loaded into a temporary table and then merged in a controlled, single-threaded operation.. Step 4: Implement retry logic with exponential backoff in the pipeline or application layer so that the aborted transaction automatically retries after a delay without requiring manual intervention.. Step 5: Review and reduce the scope or duration of long-running transactions on the affected table to minimize the window during which conflicts can occur.

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Power BI Refresh Error:
Fabric Warehouse Error 24556

What does this error mean?

A transaction using snapshot isolation was aborted because two concurrent transactions attempted to modify the same table simultaneously, causing an update conflict in the Fabric Data Warehouse. Only one transaction can proceed; the other is rolled back.

Common causes

1Two or more concurrent pipeline runs or queries attempted to UPDATE, DELETE, MERGE, or TRUNCATE the same warehouse table at the same time
2Long-running transactions holding snapshot versions overlap with other write transactions on the same table
3Uncoordinated parallel pipeline executions targeting the same destination table without write-ordering controls
4Retry logic in a pipeline triggered a second write attempt while the original transaction was still in progress

How to fix it

1Step 1: Identify the conflicting transactions by reviewing the Fabric Warehouse query activity logs to find concurrent write operations targeting the same table around the time of the error.
2Step 2: Redesign parallel pipelines to serialize writes to shared tables using pipeline dependencies, triggers, or staging tables to prevent simultaneous modifications.
3Step 3: For MERGE or UPSERT patterns, consider using a staging table approach where data is first loaded into a temporary table and then merged in a controlled, single-threaded operation.
4Step 4: Implement retry logic with exponential backoff in the pipeline or application layer so that the aborted transaction automatically retries after a delay without requiring manual intervention.
5Step 5: Review and reduce the scope or duration of long-running transactions on the affected table to minimize the window during which conflicts can occur.

Frequently asked questions

Does Fabric Warehouse automatically retry the aborted transaction?

No — Fabric Warehouse aborts and rolls back the conflicting transaction; your pipeline or application must implement its own retry logic to re-attempt the failed operation.

Can switching away from snapshot isolation prevent this error?

Snapshot isolation is the default in Fabric Warehouse and cannot be changed per-transaction in the same way as SQL Server; the recommended solution is to prevent concurrent writes to the same table through pipeline design rather than changing isolation levels.