DataGuard Apply relatively slow

Today there is an Oracle physical Dataguard apply is slow, according to the official DG optimization document to modify the relevant parameters,
The following method has a little effect, but not much.
1, modify the degree of parallelism
ALTER database RECOVER MANAGED STANDBY database PARALLEL 8 using current logfile disconnect from session;
2. Modify message size
alter system Set Parallel_execution_message_size = 4096 scope=spfile;
3. Cancel block Check
Alter system set DB_BLOCK_CHECKSUM=FALSE Scope=spfile;
4. Asynchronous IO
Alter system set DISK_ASYNCH_IO=TRUE Scope=spfile;
5, OS asynchronous transmission
Alter system set Filesystemio_options=setall Scope=spfile;
Asynch: Enable asynchronous I/O
Directio: Enable synchronous I/O
SetAll: Simultaneous asynchronous and synchronous I/O enabled
None: Disable asynchronous and synchronous I/O
(ALTER database RECOVER managed standby database cancel)

DataGuard Apply relatively slow