We have three-node AO setup in SQL Server. Primary node, one secondary node in Sync mode and another secondary node in Async mode.
Main Database on Primary node, log file-size is 434GB, Used 99.91%. Log backups is happening every hour only on Primary node.
Ran following query on Primary and Secondary servers.
SELECT log_reuse_wait_desc
FROM sys.databases
WHERE name = 'Main DB Name'
Primary node
log_reuse_wait_desc
------------------------------------------------------------
AVAILABILITY_REPLICA
Secondary-1 node (Sync mode)
log_reuse_wait_desc
------------------------------------------------------------
LOG_BACKUP
Secondary-2 node (Async mode)
log_reuse_wait_desc
------------------------------------------------------------
AVAILABILITY_REPLICA
Ran following query on Primary and Secondary servers.
SELECT log_reuse_wait_desc
FROM sys.databases
WHERE name = 'Main DB Name'
Primary node
log_reuse_wait_desc
------------------------------------------------------------
AVAILABILITY_REPLICA
Secondary-1 node (Sync mode)
log_reuse_wait_desc
------------------------------------------------------------
LOG_BACKUP
Secondary-2 node (Async mode)
log_reuse_wait_desc
------------------------------------------------------------
AVAILABILITY_REPLICA
While other DBs (much smaller than main DB) in AO groups log usage is very minimum (1 to 10%) and can be shrunk, main DB log usage continuously showing more than 99% and not shrinking.
I am guessing since log_reuse_wait_desc is showing "AVAILABILITY_REPLICA" on Primary Node, means not all the log is transferred to Secondary replica, and so its still full.
I checked Redo Queue Size in Secondary-1 Node showing 27GB, Secondary-2 is showing nothing. So most likely Secondary 1needs to get all logs from Primary. The problem is Redo Queue Size in Secondary-1 Node is increasing and not decreasing as what I through it should. Also log-file on Primary node is slowly increasing which is going to fill-up whole disk-space.