Issues Migrating Hive Metastore Tables to Unity Catalog

[vidyaKothavale]

I am in the process of migrating tables from Hive Meta store to Unity Catalog using the Databricks Labs UCX tool. After completing the assessment phase, the dashboard indicates that while external tables are ready to migrate, the managed tables are marked as "not ready." The assessment summary highlights the following findings:

1. Data is in DBFS Root

2. Unsupported cluster types (LEGACY_TABLE_ACL)

3. Unsupported DBR versions

Could the fact that the data is located in the DBFS root be the reason why the managed tables are not ready for migration?

When I run the command data bricks labs UCX migrate-table, the workflow completes successfully, but neither the external nor the managed tables appear in Unity Catalog.

I have attached a screenshot of the assessment dashboard for reference. Could these findings be the cause of the issue, and how should I proceed to resolve it?

[satya1206]

Hi @vidyaKothavale ,

What is the cost associated for UCX assessment and migration

[Amit_Dass_Chmp]

We faced the similar issue, and find out the reason was not a tool failure, but a governance and storage incompatibility.
By relocating data out of DBFS root and aligning clusters and DBRs with UC requirements, we enabled a clean, auditable, and compliant Unity Catalog migration.

Key outcome:

• Avoided unsafe auto-migration
• Established UC-aligned data ownership
• Enabled long-term governance, lineage, and access control

Our Action points :

1. Analyzed Storage Location
• Identified that Hive managed tables reside in DBFS root (dbfs:/user/hive/warehouse).
• Understood that Unity Catalog cannot govern DBFS root, as it lacks cloud‑native URIs (s3://, abfss://).
2. Validated UCX Behavior
• Confirmed UCX intentionally marks such tables as “not ready” to prevent unsafe migrations.
• UCX completes without error because it is diagnostic-first, not destructive — it skips tables that violate UC requirements.
3. Reviewed Governance Incompatibilities
• LEGACY_TABLE_ACL clusters use a permissive privilege model with DENY semantics, which cannot be auto-mapped to Unity Catalog’s strict, non‑permissive model.
• Unsupported DBRs further prevented UC registration steps.
4. Defined Correct Migration Strategy
• Recommended physically relocating managed table data from DBFS root to cloud object storage
• Registering the storage as Unity Catalog external locations or volumes
• Recreating tables under UC and applying UC-native grants