A
Troubleshooting the Standby Database

This appendix provides help troubleshooting a standby database. This appendix contains the following sections:

A.1 Problems During Standby Database Preparation

If you encounter a problem during standby database preparation, it will probably be one of the following:

A.1.1 The Standby Archive Destination Is Not Defined Properly

If the STANDBY_ARCHIVE_DEST initialization parameter is not defined as a valid directory name on the standby site, the Oracle database server will not be able to determine the directory in which to store the archived redo logs. Check the DESTINATION and ERROR columns in the V$ARCHIVE_DEST view. For example, enter:

SQL> SELECT destination, error FROM v$archive_dest;

Make sure the destination is valid.

A.1.2 The Standby Site Does Not Receive Logs Archived by the Primary Database

If the standby site is not receiving the logs, the first thing you should do is obtain information about the archiving status of the primary database by querying the V$ARCHIVE_DEST view. Check especially for error messages. For example, enter:

SQL> SELECT dest_id "ID",
  2> status "DB_status",
  3> destination "Archive_dest",
  4> error "Error"
  5> FROM v$archive_dest;

ID DB_status Archive_dest                   Error   
-- --------- ------------------------------ 
--------------------------------------
 1  VALID     /vobs/oracle/work/arc_dest/arc                          
 2  ERROR     standby1          ORA-16012: Archivelog standby database 
identifier mismatch  
 3  INACTIVE                            
 4  INACTIVE                    
 5  INACTIVE                                           
5 rows selected.

If the output of the query does not help you, check the following list of possible issues. If any of the following conditions is not met, the primary database will fail to archive to the standby site:

The service name for the standby instance is not configured correctly in the tnsnames.ora file at the primary site.
The service name listed in the LOG_ARCHIVE_DEST_n parameter of the primary initialization parameter file is incorrect.
The LOG_ARCHIVE_DEST_STATE_n parameter specifying the state of the standby archiving destination has the value DEFER.
The listener.ora file has not been configured correctly at the standby site.
The listener is not started.
The standby instance is not started.
You have added a standby archiving destination to the primary initialization parameter file, but have not yet enabled the change.
You used an invalid backup as the basis for the standby database (for example, you used a backup from the wrong database, or did not create the standby control file using the correct method).

A.1.3 You Cannot Mount the Standby Database

If any of the following conditions is not met, you cannot mount the standby database:

The standby instance is not started in NOMOUNT mode. You must first start the instance and then mount the database.
The standby control file was not created with the ALTER DATABASE CREATE STANDBY CONTROLFILE ... statement or RMAN. You cannot use the following types of control file backups:
- An operating system-created backup
- A backup created using an ALTER DATABASE statement without the STANDBY option

A.2 Problems Switching Over to a Standby Database

If you encounter a problem switching over from a primary database to a standby database, it will probably be one of the following:

A.2.1 Prepare to Switchover Fails

ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY failed with ORA-01093 error "Alter database close only permitted with no sessions connected".

This error occurs because the COMMIT TO SWITCHOVER statement implicitly closed the database and, if there are any other user sessions connected to the database, the close fails.

Action: Make sure all user sessions are disconnected from the database. You can query the V$SESSION fixed view to see what sessions are still around. For example:

SQL> SELECT SID, PROCESS, PROGRAM FROM v$session;

       SID PROCESS   PROGRAM
---------- --------- ------------------------------------------------
         1 26900     oracle@dbuser-sun (PMON)
         2 26902     oracle@dbuser-sun (DBW0)
         3 26904     oracle@dbuser-sun (LGWR)
         4 26906     oracle@dbuser-sun (CKPT)
         5 26908     oracle@dbuser-sun (SMON)
         6 26910     oracle@dbuser-sun (RECO)
         7 26912     oracle@dbuser-sun (ARC0)
         8 26897     sqlplus@dbuser-sun (TNS V1-V3)
        11 26917     sqlplus@dbuser-sun (TNS V1-V3)

9 rows selected.

In the previous example, the first seven sessions are all server background processes. Among the two SQL*Plus sessions, one is the current SQL*Plus session issuing the query, and the other is an extra session that should be disconnected before the switchover operation.

A.2.2 Startup of Second Database Fails

Suppose the standby database and the primary database reside on the same site. After both the ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY and the ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY statements are successfully executed, shut down and restart the standby database and the primary database. However, the startup of the second database fails with ORA-01102 error "cannot mount database in EXCLUSIVE mode."

This could happen during the switchover if you forget to set the LOCK_NAME_SPACE parameter in the initialization parameter file that is used by the standby database (that is, the original primary database). If the LOCK_NAME_SPACE parameter of the standby database is not set, the standby and the primary databases both use the same mount lock and cause the ORA-01102 error during the startup of the second database.

Action: Add LOCK_NAME_SPACE=unique_lock_name to the initialization parameter file used by the standby database and shut down and restart both the standby and the primary databases.

A.2.3 Archived Redo Logs Are Not Applied to the Standby Database After Switchover

The archived redo logs are not applied to the standby database after the switchover.

This may happen because some environment or initialization parameters have not been properly set after the switchover.

Action:

Check the tnsnames.ora file at the primary site and the listener.ora file at the standby site. There should be entries for a listener at the standby site and a corresponding tnsname at the primary site.
Start the listener at the standby site if it has not been started.
Check if the LOG_ARCHIVE_DEST_n initialization parameters have been set to properly archive logs from the primary site to standby site. For example, query the V$ARCHIVE_DEST fixed view at the primary site as follows:
```
SQL> SELECT DEST_ID, STATUS, DESTINATION FROM v$archive_dest;
```
If you do not see an entry corresponding to the standby site, you need to set LOG_ARCHIVE_DEST_n and LOG_ARCHIVE_DEST_STATE_n initialization parameters.
Set the STANDBY_ARCHIVE_DEST and LOG_ARCHIVE_FORMAT initialization parameters correctly at the standby site so that the archived redo logs are applied to the desired location.
At the standby site, set the DB_FILE_NAME_CONVERT and LOG_FILE_NAME_CONVERT initialization parameters. Set the STANDBY_FILE_MANAGEMENT initialization parameter to auto if you want the standby site to automatically add new datafiles that are created at the primary site.

A Troubleshooting the Standby Database