16802, 0000, "downgrading redo transport mode from SYNC disallowed"
*Cause: An attempt was made to downgrade the redo transport mode
of a standby database from SYNC to ASYNC when the configuration
was in Maximum Protection or Maximum Availability mode and the
primary database was a RAC database. This was not disallowed
even though there may have been other standby databases with redo
transport modes set to SYNC to support the protection mode.
*Action: Do one of the following if the redo transport mode of the standby
must be downgraded:
- Shut down all instances of the primary database and
restart one instance with the initialization parameter
CLUSTER_DATABASE set to FALSE. Downgrade the redo transport
mode of the standby database of interest. Then, shutdown the
instance, set the the CLUSTER_DATABASE initialization
parameter to TRUE, and restart all primary database instances.
- Downgrade the protection mode to Maximum Performance mode and
then, downgrade the redo transport mode of the standby database
of interest. Finally, upgrade the protection mode. This will
require a restart of all primary database instances if upgrading
to Maximum Protection mode.
Note that the above only works when there is at least one standby
database in the configuration that has its redo transport mode
set to SYNC.