Enable trace for SQLNET or network trace for Dataguard Environment

Enable the trace on Primary Server for check the network issue

SQL> alter system set log_archive_dest_state_2=defer;
SQL> alter system switch logfile;
SQL> alter system set log_archive_trace=4095;
SQL> alter system set log_archive_dest_state_2=enable;
SQL> alter system switch logfile;


Disable the trace on Primary Server

SQL> alter system set log_archive_dest_state_2=defer;
SQL> alter system switch logfile;
SQL> alter system set log_archive_trace=0;
SQL> alter system set log_archive_dest_state_2=enable;
SQL> alter system switch logfile;


Command give you more detail of process running during dataguard

select inst_id, process, pid, client_process, client_pid, status,thread#,sequence# from gv$managed_standby;


Note:
Tracefiles are generated in ‘TRACE_DIRECTORY_SERVER’ in SQLNET.ora
TRACK following things:
ARCs Process activity.
RFS connection.
LGWR redo shipping network activity.