Oracle Dataguard is a fantastic product. In my experience once it is configured correctly it is extremely reliable and provides for solid disaster recovery.
Dataguard is monitored by the Dataguard Broker and I usually configure this through the Enterprise Manager. Every now and then during configuration the broker configuration breaks and hangs – you cant get to the configuration page in Enterprise Manager and you get no response issuing commands via the DGMGRL command line tool.
If you find yourself in this situation you need to remove the Broker configuration manually. To do this follow the steps below.
1. Navigate to the flash_recovery_area for you database and delete the Broker configuration files. They look like ‘DR1<SID>.DAT’.
2. Log into you database as sysdba and enter the following:
alter system set dg_broker_start = false
alter system set dg_broker_start = true
You should now be able to configure the Broker through Enterprise Manager.