Option to skip log backups for databases currently automatically seeding

[transmokopter]

Description of the feature
I'm using dbo.DatabaseBackup to backup database and transaction log.
When I'm adding a new database to an availability group with automatic seeding, the automatic seeding fails because the transaction log backup run in the middle of seeding the database.
I would like to have an option to skip log backups for databases which are currently automatically seeding.

Something like this:

EXEC dbo.DatabaseBackup 
  @Databases = 'AVAILABILITY_GROUP_DATABASES',
  @BackupType = 'LOG',
  @AutomaticSeedingAction = 'SKIP_DATABASE'

And in dbo.DatabaseBackup, check sys.dm_hadr_physical_seeding_stats, to see if the database is currently auto-seeding (end_time_utc IS NULL would, I guess, be a good check).

[olahallengren]

As I understand it, SQL Server should not truncate the log until the automatic seeding has completed.

"During seeding, the transaction log on the database at the primary replica continues to grow and cannot be truncated until automatic seeding of that database is complete."
https://learn.microsoft.com/en-us/sql/database-engine/availability-groups/windows/automatic-seeding-secondary-replicas?view=sql-server-ver16

Could I ask about the error message you're getting and which version of SQL Server you're running? Can you open a support case with Microsoft?

[transmokopter]

It’s on SQL Server 2022. I will replicate the error and get back about the exact error.

I’m not sure the log is truncated, but automatic seeding operation somehow gives up if there was a transaction log backup taken between when seeding started and when active log portion is to be replicated.

[CommanderBond]

I confirm this behavior with SQL Server versions from 2016 to 2022 (we didn't auto-seed with SQL Server 2025 yet).
We are always disabling the transaction log backup jobs during seeding operations. It happens far too often that (long) seeding is stalled if a transaction log backup occurs until seeding is done (but it doesn't always break the seeding, sometimes it's working even if transaction log backus occur).

[olahallengren]

Thank you @transmokopter and @CommanderBond.

It's not good that you can't run log backups, while the seeding is going on. For a large database this can take many hours.

I would say this is a bug in SQL Server that should be fixed.

Would it be possible for you to open a support case with Microsoft, preferrable on SQL Server 2022 that is still in mainstream support? I would also be happy to help in the conversation with Microsoft.

[CommanderBond]

Yes, we know the implications of not taking transaction log backups for hours. Since we are also seeding via Distributed AGs to a remote location with limited network bandwidth, we are familiar with hours-long seeding times.

We worked around the nasty stall issue by disabling the job, but we didn't report it as a bug yet (if it was a bug).

Seems to be pretty common not to take transaction log backups during seeding operations. I remember that I read it on a website once, but I can't remember where exactly.