Error 12154 received logging on to the standby

There are several error messages related to dataguard environment and many of them have been discussed in my blog, and you can find links to those articles at the bottom of this article. In this article, I will explain Error 12154 that I received in one of my dataguard environments. This error message may appear in the alert log file of your primary database and it would seem similar to the following.

Error 12154 received logging on to the standby FAL[client, USER]: Error 12154 connecting to <FAL_SERVER> for fetching gap sequence

FAL[client, USER]: Error 12154

If you see this error message in alert log file of primary database. Check following points.

• Check if your standby database is up and running and is registered with the Listener?
• Check the value of parameter “FAL_SERVER” initialization parameter in standby database, and use “tnsping <FAL_SERVER>” on standby host to confirm if primary database is accessible through FAL_SERVER TNS entry form standby database.
• Make sure that password file is present on standby and it is exact copy of primary database. In case of RAC, make sure that all primary RAC nodes have exact copy of password file and also same password file is copied on all standby RAC nodes.
• Check whether environment variable TNS_ADMIN is set to a correct value and TNSNAMES.ORA file exists at the location set for this variable. To confirm that TNS_ADMIN was set correctly when database was started, execute following steps.
  
  

  [root~]# ps -ef|grep pmon -- Above command would return you process ID of pmon process for the datavase. Suppose Process ID for pmon is 87987, execute following command to check all environment variables set for pmon. [root~]# ps eww 87987

  
  In the output of last command shown above, you can check if TNS_ADMIN has a correct value. If not, you may restart the database with correct environment variable, or alternatively you can create TNSNAMES.ORA file at this TNS_ADMIN location with correct TNS service entry that points to the standby database

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