Oracle Error Codes

downgrading redo transport mode from SYNC disallowed

An attempt was made to downgrade the redo transport mode of a standby database from SYNC to ASYNC or ARCH when the configuration was in Maximum Protection or Maximum Availability mode and the primary database was a RAC database. This is not allowed, even if there are other standby databases with log transport modes set to SYNC to support the data protection mode.

How to Solve :

You can do one of the following if you need to downgrade the redo transport mode of the standby database: (1) Shut down all instances of the primary database and restart one instance with initialization parameter CLUSTER_DATABASE set to FALSE. Downgrade the redo transport mode, shutdown the instance, and restart all instances with CLUSTER_DATABASE set to TRUE. (2) Downgrade the protection mode to Maximum Performance mode first. Then downgrade the redo transport mode, then upgrade the protection mode again (which involves a shutdown and restart of the primary database). Note that the above only works when there exists at least one more standby database in the configuration that has the log transport mode set to SYNC.