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SQL differential backup runs as full due to backup start time mismatch

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This article applies to:

  • Product edition: Phoenix

Problem description

The SQL differential backup runs as full due to a backup start time mismatch error. The Phoenix agent scans all the databases selected for backup in the backup set, even if one of those has been backed up by a third party or native backup software. Note that while the scan is a full scan, the upload will still be differential.


In each differential backup, Phoenix matches the current (system) database backup start time v/s the saved database backup start time (Phoenix metadata, saved with last full backup). If there is a mismatch, Phoenix converts it to full. 

This mismatch occurs in one of the following cases:

  • There is a third-party backup or MS-SQL native backup (non-Phoenix backup) running on the Server .
  • The database was deleted and a new database was created with the same name on the instance.
    Where instance name : ABCNODE-02:
    DB name : PAF


Log locationC:\ProgramData\Phoenix\SQL\log\backup\<backupsetID>
You can also download and extract the logs.

[2019-03-19 01:00:44,970] [INFO] [Tid:<_MainThread(MainThread, started 10196)>] Backup start time mismatch for [ABCNODE-02:PAF] found 
[2019-03-19 01:00:44,970] [INFO] [Tid:<_MainThread(MainThread, started 10196)>] Backup start time mismatch found, converting to full 


Perform any one of the following tasks:

  • Disable any third-party backups running on the MS-SQL DB, including  SQL native backups.
  • Create another backup set for the same SQL server for this specific database.
    Note:  To create a new backup set, you must uncheck the DB from the current backup set.
  • Perform "Copy-only" native backups from the SQL server if disabling backups through third-party or native backups is not possible.