Backup Sets containing SQL database backups may expire prematurely.

Problem

Baseline SQL full or prior incremental backups may expire even when it has some unexpired incremental backups dependent on it. This issue may occur when all of the following conditions are met:

1) User databases are backed up in the same backup job with the SQL System databases (Master, Model, MSDB).
2) Both Full and Incremental (Automatic or Differential (block level) or incremental (block level)) backup types are being performed of the SQL instance.
3) The retention period of the full backup or earlier incremental backup has expired
4) A depending incremental or differential backup set has not yet expired.

In this scenario when the Incremental SQL backups are run, the SQL system databases will automatically be switched to 'full' backups in a new backup set since non-full backup types are not possible on system databases. MS Article. This switch to a ‘full’ backup creates a new backup set chain within Backup Exec, breaking the dependencies of all the selected databases in this backup job, including User databases. The previous SQL Incremental backup sets will no longer depend on the prior ‘full’ or prior ‘incremental’ backups. If the ‘full’ or prior ‘incremental’ backup set expires, it may be deleted, as the recovery chain protecting those sets is broken.
 

Cause

When the system databases are automatically switched to a full backup method during an incremental backup job, it removes the dependency on the prior backups from the associated user database backup set.  Since the prior full and incremental backups are no longer part of the dependency chain, they can be deleted if the retention period expires before the depending incremental backups.

Solution

Etrack : 3916580