ORA-16857: member disconnected from redo source for longer than specified threshold

ORA-16857: member disconnected from redo source for longer than specified threshold

Parameter used to get this warning error is TransportDisconnectedThreshold Parameter. It value defined in seconds.
Default value : 30 seconds, We can also set the parameter to zero value to disable the alert.

Increase the value in DG broker service

EDIT DATABASE testfo SET PROPERTY TransportDisconnectedThreshold='120';

On Oracle Error

C:\Oracle>oerr ora 16857
16857, 00000, "member disconnected from redo source for longer than specified threshold"
// *Cause: The amount of time the member was disconnected from the redo source
// exceeded the value specified by the TransportDisconnectedThreshold
// configurable database property. It is caused by a lack of network
// connectivity between the redo source and the member.
// *Action: Ensure that there is network connectivity between the redo source
// and the member and that the redo source is working properly.

Solution for fixed the problem
In one of our environment we are getting this error, On checking the redo files

Two possible causes:
1. we are found SIZE different in standby and online redo log file.
2. Check the THREAD# parameter value is same for all. Otherwise drop and create new redo same as size.

Check the Size of Standby and Redo logs on Both Server Primary and Standby machines:

SQL> select GROUP#,THREAD# ,BYTES/1024/1024 from v$standby_log;

GROUP# THREAD# BYTES/1024/1024
---------- ---------- ---------------
4 1 50
5 1 50
6 1 50
7 1 50

SQL> select GROUP#,THREAD#,BYTES/1024/1024 from v$log;

GROUP# THREAD# BYTES/1024/1024
---------- ---------- ---------------
1 1 100
3 1 100
2 1 100

Note: Size of standby files is 50 MB and Redo log file is 100 MB
Then we need to drop the standby files and create new file with size 100 MB.

Example

-- Stop the recovery
SQL> alter database recover managed standby database cancel;

--Drop the redo group
ALTER DATABASE DROP STANDBY LOGFILE GROUP 4;

--Add the size
SQL>alter database add standby logfile thread 1 group 4 size 100m;

--Start the recovery
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE THROUGH ALL SWITCHOVER DISCONNECT USING CURRENT LOGFILE;

Note: For more detail, Please follow the links: Steps to Resize Standby Redolog Files

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