This most often occurs with traditional Forward Incremental, and rarely occurs with Forward-Incremental-Forever and Reversed Incremental rarely have this issue. Traditional Forward Incremental occurs when the Synthetic or Active Full option is enabled within a job, or an active full is manually generated via the job’s context menu.
The most common causes are:C1. Expected effect of how retention is enforced with traditional forward incremental. The following articles should be read to understand this in depth:
C2. Not enough free space for a new full backup to be created. This is often caused by a misunderstanding regarding the number of full restore points a job will be required to maintain. For a job that is configured to have a weekly full restore point, you will need 1 full point for every 7 restore points set in retention, plus 1. A job that is set for 14 restore points will have a maximum of 3 full restore points, assuming the job runs daily.C3. The Transform/Merge fails to process or the Synthetic full fails to be created. This often occurs due to:
- Due to poor storage I/O performance. The common resolution is to switch to using the periodic active full option.
- Not enough overhead free space to perform these type tasks.
Note: If the synthetic full backup fails and the retry begins on a day that the synthetic full is not scheduled, the job session will start, determine that there are no incremental VM tasks to retry and that a synthetic full is not scheduled, and then stop. This empty job session will be marked as a success because no errors occurred.
C4. The job did not perform the full or transform operation as scheduled. This often occurs due to:
C5. Retention could not be enforced because the storage refused to allow the delete operation.C6. Anti-Virus prevents Veeam deleting or modifying existing backup files.
- The job being disabled on that day.
- An incremental job session ran for more than 24 hours causing the job not to start on the scheduled day. For example, the full is scheduled for Saturday, but the incremental session that began Friday ran for more than 24 hours, so the next job session did not start until Sunday.
- The Veeam Backup & Replication software was installed within an OS that was configured to sleep after a period of time causing the OS to be asleep at the time the job was to run.
- The jobs are set to run in sequence, and the previous job ran past midnight causing this job to not run on the scheduled day for fulls. For example, the full is scheduled for Saturday, but the job is scheduled to run after a previous job completes, and so did not start until Sunday.