Expdp is not possible while standby database is in "read only with apply"
Reason: every datapump job will create master table in database to track the job status. So the database is in readonly it cannot create master table in database and throw error.
[oracle@localhost app]$ expdp \'/as sysdba\' directory=dump dumpfile=test.dmp logfile=test.log tables=ramesh.test
Export: Release 12.2.0.1.0 - Production on Sun Aug 12 13:12:01 2018
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Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
ORA-31626: job does not exist
ORA-31633: unable to create master table "SYS.SYS_EXPORT_TABLE_05"
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 95
ORA-06512: at "SYS.KUPV$FT", line 1161
ORA-16000: database or pluggable database open for read-only access
ORA-06512: at "SYS.KUPV$FT", line 1054
ORA-06512: at "SYS.KUPV$FT", line 1042
