Starting with SQL Server 2019 Cumulative Update 5 (CU5), setting MAXTRANSFERSIZE largerthan 64KB is no longer required to enable theoptimized compression algorithm with Transparent Data Encryption (TDE) encrypted databases. If the backupcommand is specified WITH COMPRESSION or the backup compression default server configuration isset to 1, MAXTRANSFERSIZE willautomatically be increased to 128K to enable the optimized algorithm. If MAXTRANSFERSIZE is specified on the backup command with a value > 64K, theprovided value will be honored. In other words, SQL Server will neverautomatically decrease the value, it will only increase it. If you need to backup a TDE encrypted database with MAXTRANSFERSIZE = 65536, you must specify WITH NO_COMPRESSION or make sure that the backup compression default serverconfiguration is set to 0.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This improvement is included in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server: