The 'log_reuse_wait_desc' column helps determine why the log file is not shrinking.By querying the sys.databases table, the 'log_reuse_wait_desc' value for a database can be checked.In the case mentioned, the 'log_reuse_wait_desc' value was 'AVAILABILITY_REPLICA', indicating replication of transactions.Once the 'log_reuse_wait_desc' changes to 'ACTIVE_TRANSACTION', the log file can be shrunk.