Azure Cosmos DB Mirroring in Fabric – Internal System Error, 0 Rows Replicated (STG vs PRD)

Hi DiegoF93,

Note: This response was enhanced with the assistance of an AI tool. The information has been verified against the official Microsoft Fabric documentation.

This pattern mirroring stuck at "Running" with 0 rows and a frozen "Last completed" after a stop/start cycle is a known transient state with Cosmos DB mirroring. The root cause is usually a stale internal Change Feed checkpoint that doesn't reset cleanly on restart.

A few targeted things to try:

1. Delete and recreate but wait 10+ minutes before recreating
The internal Change Feed lease container in Cosmos needs time to fully release after a stop. If you recreate too quickly, the new mirror picks up a corrupted lease state. Wait at least 10 minutes after deleting before creating a new one.

2. Check the Cosmos DB Change Feed lease container
Fabric Mirroring uses the Cosmos DB Change Feed internally. Go to your Cosmos account → Data Explorer → look for a container named _fabric_mirror_leases or similar. If it exists and has stale documents, delete them before recreating the mirror.

3. STG vs PRD check if it's a network/firewall difference
Since PRD works but STG doesn't, verify that STG's Fabric capacity has the same network access to Cosmos DB (no VNet restrictions, IP allowlist includes Fabric East US egress IPs).

4. Open a support ticket with the ArtifactId
The Internal system error with a specific ArtifactId means the error is logged server-side at Microsoft. File a support request referencing that ArtifactId the Fabric team can trace the exact failure from their telemetry.

Note: This response was drafted with AI assistance and reviewed/validated before posting.

Docs: Troubleshoot Fabric mirrored databases 

Hi DiegoF93 

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