---
type: concept
x-llmwiki:
  schemaVersion: "0.1"
  contentHash: fea762167881098f5d34a3d6572a18caaa22c3736b4c530dda40a7bd32d7007a
  pageDirectory: concepts
  sources:
    - delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md
  confidence: 0.85
  provenanceState: inferred
  freshnessStatus: unverified
  aliases:
    - deltalog-version-mismatch
    - DVM
  citations:
    - file: delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md
title: DeltaLog Version Mismatch
description: A condition where the internal managed DeltaLog and external DeltaLog have diverging versions, preventing table rollback
tags:
  - databricks
  - delta-lake
  - metadata
timestamp: "2026-06-19T18:21:54.304Z"
---

#DeltaLog Version Mismatch

**DeltaLog Version Mismatch** is a specific error condition that occurs when the [DeltaLog] versions between a managed table and its external counterpart differ. It is raised as one of the sub‑errors under the [`DELTA_ALTER_TABLE_UNSET_MANAGED_FAILED` error class](delta-alter-table-unset-managed-failed-error-class). ^[delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md]

## Cause

The error appears when an `ALTER TABLE tbl UNSET MANAGED` command is run, but the managed DeltaLog version (`<managedDeltaLogVersion>`) does not match the external DeltaLog version (`<externalDeltaLogVersion>`). This usually happens because a concurrent `ALTER TABLE` `UNSET MANAGED` command has already successfully rolled the table back to an [External Table], and the DeltaLog versions have diverged. ^[delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md]

## Context

The `DELTA_ALTER_TABLE_UNSET_MANAGED_FAILED` error class includes several possible sub‑conditions. The specific sub‑error reported includes the actual version numbers to help diagnose the mismatch:

```
VERSION_MISMATCH
The versions of the managed DeltaLog (<managedDeltaLogVersion>) and external DeltaLog (<externalDeltaLogVersion>) do not match.
```

^[delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md]

Other sub‑conditions in the same error class — such as `TIME_WINDOW_EXCEEDED`, `TRUNCATED_HISTORY`, or `UNEXPECTED_ERROR` — are unrelated to the version mismatch itself. The version mismatch specifically points to a concurrent table conversion that altered the DeltaLog state. ^[delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md]

## Related Concepts

- DeltaLog – The transaction log for Delta Lake tables.
- [Managed Table](/concepts/unity-catalog-managed-tables.md) vs External Table – The conversion between these table types triggers the error.
- ALTER TABLE – The DDL command used to unset the managed status.
- [Unity Catalog](/concepts/unity-catalog.md) – Managed tables are migrated to Unity Catalog; rollback from managed to external is only supported within a time window.
- DELTA_ALTER_TABLE_UNSET_MANAGED_FAILED error class – The parent error class containing this condition.

## Sources

- delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md

# Citations

1. [delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws.md](/references/delta_alter_table_unset_managed_failed-error-condition-databricks-on-aws-a24f2e75.md)
