During the DataPump export process, if the relevant session is waiting for the following message, you can resolve this issue by doing the following operations.
“wait for unread message on broadcast channel”
The following commands update related statistics.
SQL> EXEC DBMS_STATS.GATHER_FIXED_OBJECTS_STATS (NULL);
SQL> EXEC DBMS_STATS.GATHER_DICTIONARY_STATS;
SQL> EXEC DBMS_STATS.GATHER_SYSTEM_STATS;