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This article is about how to resolve two error states of oracle11gR2 DataGuard switchover. Xiaobian thinks it is quite practical, so share it with everyone for reference. Let's follow Xiaobian and have a look.

Oracle11gR2 DataGuard was built in the company's test environment for pre-production testing. There are two types of redundant switching in Data Guard, one is failover lossless switching and the other is failover discard switching.

The so-called switchover is for failover, it is a lossless handover, the process of switching will not lose data. It is possible to make the main and standby interchangeable smoothly and both libraries can be used normally. Switching process: main library-> switching-> standby library-> check status-> original and standby library-> switching-> main library-> check status again

Application: The master library needs to be adjusted and upgraded due to performance or other reasons. In this case, the new master library can be used to provide services to the outside world after switching.

DG on the building process will not be detailed here, the following on the switching process occurred in the two error states for analysis and resolution.

I. SWITCH LATENT STATUS

Query database roles and status on backup

SYS@standby> select database_role,switchover_status,open_mode from v$database;

DATABASE_ROLE SWITCHOVER_STATUS OPEN_MODE

---------------- -------------------- --------------------

PHYSICAL STANDBY SWITCHOVER LATENT READ ONLY

Switchover Latent rather than to Primary

The problem is that the switch is in pending mode and cannot be returned to the main library until it is completed. When you check the ALERT log, you don't see any errors. Do you want to wait? In fact, there is no need to wait. The reason for this problem is that the log is not archived, so the backup database is inconsistent with the main database and needs to be restored. When the backup database is restored to be consistent with the primary database, the status becomes to_primary.

To verify that the problem is not the cause of the above, you can continue to execute the following sentence on the backup library

sys@standby> ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN;

ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY WITH SESSION SHUTDOWN

*

ERROR at line 1:

ORA-16139: media recovery required

Media recovery is required.

According to the above analysis and positioning, we need to solve this problem, we need to cut off the application on the backup library and enable log synchronization.

SYS@standby> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

Database altered.

SYS@standby> SELECT SWITCHOVER_STATUS FROM V$DATABASE;

SWITCHOVER_STATUS

--------------------

TO PRIMARY

It is displayed as TO PRIMARY, and the status is normal at this time.

SYS@standby> alter database commit to switchover to primary with session shutdown;

Database altered.

SYS@standby> select database_role,switchover_status,open_mode from v$database;

DATABASE_ROLE SWITCHOVER_STATUS OPEN_MODE

---------------- -------------------- --------------------

PRIMARY NOT ALLOWED MOUNTED

open the database

sys@standby>alter database open;

Switch to the journal.

sys@standby> alter system switch logfile ;

System altered.

Check the status of the logs again.

SYS@standby> select sequence#,standby_dest,archived,applied,status from v$archived_log;

SEQUENCE# STA ARC APPLIED S

---------- --- --- --------- -

4 NO YES YES A

5 NO YES YES A

6 NO YES YES A

7 NO YES YES A

8 NO YES YES A

9 NO YES YES A

10 NO YES YES A

11 NO YES YES A

11 NO YES YES A

10 NO YES YES A

12 NO YES YES A

Yes, it's already synchronized.

II. FAILS DESTINATION STATUS

When the backup library is switched to the master library, the switching status is found to be FAiled DESTINATION.

SYS@primary> select database_role,switchover_status,open_mode from v$database;

DATABASE_ROLE SWITCHOVER_STATUS OPEN_MODE

---------------- -------------------- --------------------

PRIMARY FAILED DESTINATION READ WRITE

FAILED DESTINATION, NOT TO STANDBY

This problem indicates that there is a problem with the connection between the main library and the backup library. You can check the ALERT log to see what is going on.

Error 12541 received logging on to the standby

Check whether the listener is up and running.

Errors in file /u01/app/oracle/diag/rdbms/primary/primary/trace/primary_arc2_2546.trc:

ORA-12541: TNS:no listener

PING[ARC2]: Heartbeat failed to connect to standby 'standby'. Error is 12541.

This shows that there is a problem with the monitoring of the backup library. Restart the monitoring of the backup library. Check again and the status will change to standby.

SYS@primary> select database_role,switchover_status,open_mode from v$database;

DATABASE_ROLE SWITCHOVER_STATUS OPEN_MODE

---------------- -------------------- --------------------

PRIMARY TO STANDBY READ WRITE

Of course, there are many reasons for FAILS DESTINATION, such as the attribute value of log_archive_dest_2 parameter, configuration error of password file or permission problem, etc.

In short, there is a problem, face the problem analysis problem on the right, from which you can learn a lot.

Meaning of Switchover_Status value attached

NOT ALLOWED

The current database is not a primary database with a standby database

PREPARING DICTIONARY

The logical standby database is sending its redo data to a primary database and other standby databases in preparation for the switchover

PREPARING SWITCHOVER

When accepting redo data for a switchover, logical standby configurations use it

RECOVERY NEEDED

The standby database has not yet received a handoff request.

SESSIONS ACTIVE

Active SQL sessions exist in the primary database; these sessions must be disconnected before execution can continue

SWITCHOVER PENDING

For standby databases that have received a primary database switch request but have not yet processed it

SWITCHOVER LATENT

The switch is not complete and returns to the main database

TO LOGICAL STANDBY

The primary database has received the complete dictionary from the logical standby database

TO PRIMARY

the standby database can be convert to that primary database

TO STANDBY

The primary database can be converted to a standby database

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