I have a 2 node WSFC and I have SQL Server 2017 synchronous AG with automatic failover.
My log file keeps on growing despite frequent successful log backups and dbcc sqlperf('logspace') shows 99.9% of space is used and the log is not getting truncated.
There are no long running open transactions transactions in my primary and we use secondary only to offload backup workload.
log_reuse_wait_desc shows AVAILABILITY_REPLICA. My secondary replica is fully synchronized and log_send_queue and redo_log_queue size are normal.
I can only see a full backup in progress in my secondary which is running for more than 2 days.
Does a long running active full backup in secondary replica does not allow truncation of logs because sql engine needs the log information from the start of the full backup operation for successful completion of a consistent backup