Introduction

The TestUC2003 – Metastore Assignment Failed error occurs when Databricks fails to assign a Unity Catalog metastore to a workspace. This error prevents Unity Catalog from functioning and can block operations like creating catalogs, accessing schemas, and managing tables.

🚨 Common symptoms of TestUC2003:

• “TestUC2003 – Metastore Assignment Failed” error while assigning the metastore.
• Cannot create or access catalogs and schemas.
• Cluster and SQL Warehouses fail to recognize the metastore.
• Unity Catalog is visible, but operations return metastore-related errors.

Common Causes and Fixes for TestUC2003

1. Incorrect Metastore Configuration or Missing Metadata

Symptoms:

• Error: “Metastore not found” when trying to assign it to a workspace.
• SHOW METASTORES returns no results.

Causes:

• Metastore was not created properly or does not exist in the current workspace.
• The metastore ID is incorrect or points to a non-existent resource.

Fix:
✅ Verify if the metastore exists:

SHOW METASTORES;

✅ If the metastore is missing, create it:

databricks unity-catalog metastores create --name my-metastore --region <region> --s3-bucket <bucket-name>

✅ Assign the correct metastore to the workspace:

databricks unity-catalog metastores assign --metastore-id <metastore-id> --workspace-id <workspace-id>

✅ Verify the assignment:

SHOW METASTORES;

2. Insufficient Permissions for Metastore Assignment (AWS and Azure)

Symptoms:

• Error: “Permission denied: Cannot assign metastore to workspace.”
• Cluster and jobs fail to access Unity Catalog tables.

Causes:

• AWS IAM role or Azure service principal lacks necessary permissions for Unity Catalog resources.
• User attempting the assignment lacks admin privileges in Databricks.

Fix:

AWS Fix:

✅ Ensure the IAM role has Glue and S3 access permissions:

{
  "Effect": "Allow",
  "Action": [
    "glue:GetCatalog*",
    "s3:GetObject",
    "s3:ListBucket",
    "s3:PutObject"
  ],
  "Resource": "*"
}

✅ Update IAM policy and attach it to your workspace:

aws iam put-role-policy --role-name <role-name> --policy-name UnityCatalogPolicy --policy-document file://policy.json

Azure Fix:

✅ Grant the correct role to the service principal:

az role assignment create --assignee <service-principal-id> --role "Storage Blob Data Contributor" --scope /subscriptions/<sub-id>/resourceGroups/<rg>/providers/Microsoft.Storage/storageAccounts/<storage-name>

✅ Verify Key Vault permissions:

az keyvault set-policy --name <keyvault-name> --spn <service-principal-id> --secret-permissions get list

3. Workspace and Metastore Region Mismatch

Symptoms:

• Error: “Metastore region does not match workspace region.”
• Cannot assign metastore to workspace.

Causes:

• Unity Catalog requires that the metastore and workspace be in the same cloud region.
• Cross-region configurations are not supported.

Fix:
✅ Check the region of your workspace and metastore:

databricks workspace get-status

✅ Create the metastore in the same region as your workspace:

databricks unity-catalog metastores create --region <workspace-region> --s3-bucket <bucket-name>

✅ Reassign the metastore:

databricks unity-catalog metastores assign --metastore-id <new-metastore-id> --workspace-id <workspace-id>

4. Existing Hive Metastore Conflicts

Symptoms:

• Error: “Conflicting metastore detected.”
• Cannot migrate or assign Unity Catalog metastore.

Causes:

• The workspace is already using a legacy Hive metastore.
• Unity Catalog cannot be assigned until the Hive metastore is removed.

Fix:
✅ Convert Hive tables to Delta format and migrate to Unity Catalog:

ALTER TABLE hive_metastore.default.my_table CONVERT TO DELTA;

✅ Detach the legacy Hive metastore and assign Unity Catalog:

databricks unity-catalog metastores assign --force --metastore-id <metastore-id> --workspace-id <workspace-id>

5. Network or Connectivity Issues

Symptoms:

• Error: “Unable to connect to metastore service.”
• Metastore assignment fails intermittently.

Causes:

• VPC or firewall rules block access to Unity Catalog services.
• Network latency or DNS resolution issues in the Databricks workspace.

Fix:
✅ Ensure that network settings allow access to Unity Catalog services:

• Open ports for Unity Catalog traffic (TCP 443).
• Use AWS PrivateLink or Azure Private Endpoints for secure connectivity.

✅ Test network connectivity to cloud storage:

nc -zv s3.amazonaws.com 443
az network private-endpoint show --name <endpoint-name>

Step-by-Step Troubleshooting Guide

Step 1: Verify Metastore Status

SHOW METASTORES;

Step 2: Check IAM and Role Permissions

aws iam get-role --role-name <role-name>
az role assignment list --assignee <service-principal-id>

Step 3: Ensure the Workspace and Metastore Are in the Same Region

databricks workspace get-status

Step 4: Resolve Any Network or Connectivity Issues

ping <databricks-endpoint>

Best Practices to Avoid TestUC2003 – Metastore Assignment Failed

✅ Ensure Consistent Region for Workspace and Metastore

• Keep both the workspace and metastore in the same region.

✅ Grant Necessary Permissions to IAM Roles or Service Principals

• Ensure AWS Glue, S3, and Azure Storage Blob roles are correctly assigned.

✅ Avoid Conflicts With Legacy Hive Metastore

• Migrate Hive Metastore tables to Unity Catalog before assigning the new metastore.

✅ Monitor Network and Connectivity for Unity Catalog Services

• Use PrivateLink or Private Endpoints for secure access.

Conclusion

The TestUC2003 – Metastore Assignment Failed error in Databricks Unity Catalog typically arises from misconfigured metadata, insufficient permissions, region mismatches, or network connectivity issues. By following the steps in this guide—verifying metastore status, checking permissions, ensuring region compatibility, and resolving conflicts—you can successfully assign the metastore and enable Unity Catalog for your workspace.