文档解释
ORA-16802: 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.
ORA-16802错误指出尝试从同步重做传输模式降级失败。
官方解释
ORA-16802: downgrading redo transport mode from sync disallowed
表达的具体意思是，尝试从同步重做传输模式降级失败。当您使用ALTER DATABASE RECOVERY {MANAGED|UNMANAGED}命令将数据库从管理模式恢复到未管理模式时，可能会发生此错误。
常见案例
ORA-16802通常会在数据库恢复模式从管理模式切换到未管理模式时出现。
一般处理方法及步骤
1. 使用ALTER SYSTEM SET log_archive_dest_state_2 = DEFER e来推迟传输模式的降级。
2. 将数据库恢复模式从管理模式切换到未管理模式，例如，ALTER DATABASE RECOVERY {MANAGED|UNMANAGED}。
3. 将log_archive_dest_state_2返回到它的默认值。
