You have 2 options

Option 1) Use a network link, eg this from MOS note 1356592.1



In this Document
Goal
Solution
Prerequisites
Steps to execute to export from Physical Standby Database
Typical Errors when exporting from Physical Standby databases


Applies to:
Oracle Database - Enterprise Edition - Version 10.1.0.2 and later
Information in this document applies to any platform.
***Checked for relevance on 01-Feb-2016***
Goal

This document describes how to successfully execute DataPump Export to export data from a Physical Standby database.
Solution
Prerequisites

It's important to know that Data Pump Export (expdp) cannot be executed directly on the Physical Standby database. This is due to the fact that Data Pump Export needs to create and maintain a Master Table which requires that a database would be open in "READ WRITE" mode. Therefore it is necessary to connect from a "non-Standby" database (which will maintain the Master Table) to the Physical Standby database using parameter NETWORK_LINK.

The NETWORK_LINK parameter initiates an export by using a valid database link. This means that the system to which the expdp client is connected contacts the Physical Standby database referenced by the source_database_link, retrieves data from it, and writes the data to a dump file set back on the connected system.

The Physical Standby database must be opened in "READ ONLY" mode.

Steps to execute to export from Physical Standby Database

Physical Standby Database

-- Connect to Physical Standby database and check its status

SQL> select instance_name, status from v$instance;

INSTANCE_NAME STATUS
---------------- ------------
PHYSTBY MOUNTED

-- Cancel managed recovery and open database in "READ ONLY" mode.
SQL> alter database recover managed standby database cancel;
SQL> alter database open read only;


-- Verify database status

SQL> select instance_name, status from v$instance;

INSTANCE_NAME STATUS
---------------- ------------
PHYSTBY OPEN


SQL> select open_mode from v$database;

OPEN_MODE
--------------------
READ ONLY

"Non Standby" Database

-- create DB Link, Oracle Directory and test it

SQL> create database link expdp_primary connect to system identified by password using ‘standby_database’;

SQL> select db_unique_name from v$database;

SQL> select db_unique_name from v$database@expdp_primary;

SQL> create directory datapump as ‘/tmp’;


-- Use NETWORK_LINK to database link above to connect to the Physical Standby database:

expdp system/password directory=datapump network_link=expdp_primary full=y dumpfile=standby_database.dmp logfile=standby_database.log



Option 2)

Open the standby in "snapshot standby" mode (it becomes read/write), then take your export, then revert it back to standard standby mode (which will automatically flash it back and resume sync with the primary).

- ALTER DATABASE CONVERT TO SNAPSHOT STANDBY;
- run your export
- ALTER DATABASE CONVERT TO PHYSICAL STANDBY;

(Note - that is not the complete list of steps, but its easy enough to put a script together to do this)

Hope this helps.