max protection ADG 最大保护模式

max protection 有没有必要？ 由于有SRL实时apply存在，只要监控好同步就可以，不必要将Primary置于险境.

4. Differents in the Log Apply Services when using Standby Redo Logs
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In case you do not have Standby Redo Logs, an Archived Redo Log is created by the RFS process and when it has completed,
 this Archived Redo Log is appliedto the Standby Database by the MRP (Managed Recovery Process) or the Logical
Apply in Oracle 10g when using Logical Standby. An open (not fully written) ArchiveLog file cannot be applied on the 
Standby Database and will not be used in a Failover situation. This causes a certain data loss.
redo apply 一个一个archive log file apply ，没有写满不会apply 

If you have Standby Redo Logs, the RFS process will write into the Standby Redo Log as mentioned above and when a
 log switch occurs, the Archiver Process of the Standby Database will archive this Standby Redo Log to an Archived Redo Log,
while the MRP process applies the information to the Standby Database.  In a Failover situation, you will also have access to the 
information already written in the Standby Redo Logs, so the information will not be lost.

Starting with Oracle 10g you have also the Option to use Real-Time Apply with Physical and Logical Standby Apply. 
When using Real-Time Apply we directly apply Redo Data from Standby RedoLogs. Real-Time Apply is also not able to apply Redo
from partial filled ArchiveLogs if there are no Standby RedoLogs. So Standby RedoLogs are mandatory for Real-Time Apply.

NOTE : In 12c DEFAULT MRP will go to REAL TIME APPLY mode.

Default Standby recovery in REAL time apply.
      SQL>alter database recover managed standby database disconnect;

To Start MRP in non real time apply mode use,(in 12c)
       SQL>alter database recover managed standby database using archived logfile disconnect;

5. Standby RedoLogs and the Data Guard Broker
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If there is an active Data Guard Broker Configuration on this Data Guard Environment the following Error can be raised 
in the Data Guard Broker Configuration if the setup Transport Method (LogXptMode) is 'SYNC' or 'ASYNC'
and there are no Standby RedoLogs configured:

Warning: ORA-16809: multiple warnings detected for the database

In the corresponding DRC.LOG-Files and the Database Status you can find: 

 ORA-16789: standby redo logs not configured

-> So please add corresponding Standby RedoLogs to the Standby Database. 
As per default the Data Guard Broker tries to start Log Apply Services in Real-Time Apply Mode which is not possible without Standby RedoLogs.
Note that starting with Oracle 11g ARCH Log Transport Method is deprecated.