9 Troubleshooting Data Guard

9.2.1 ORA-16596: database not part of the Data Guard broker configuration

A request was issued to the broker, but the database instance through which you have connected is no longer a part of the broker configuration. You may see this error when the broker fails to locate a broker configuration profile for the database upon which it is running.

Solution Reconnect to the configuration through another database that you know is part of the broker configuration. Confirm that a database exists in the broker configuration that has a name that matches the db_unique_name value of the database that returned the ORA-16596 error.

This problem can also occur if you attempt to enable a configuration, but the broker configuration file for one of its databases was accidentally removed or is outdated. In this case, remove the database from the broker configuration, manually delete the configuration file for that standby database (not for the primary database), and try again to enable the configuration. After the configuration is enabled, to create a new database profile for the previously deleted standby database, you can either use the Enterprise Manager Add Standby Database wizard and choose the Add existing standby database option, or you can use the DGMGRL command-line interface and issue the ADD DATABASE command.

9.2.2 Redo Accumulating on the Primary Is Not Sent to Some Standby Databases

By viewing the Log File Details page in Enterprise Manager, you have determined that log files are accumulating on the primary database and are not being archived to some of the standby databases in the broker configuration.

Solution To narrow down the problem, do the following:

• Verify that the state of the primary database is in the TRANSPORT-ON state (not TRANSPORT-OFF).

• Verify that the value of the LogShipping database property of the standby database in question is ON.

• Check the status of the redo transport services on the primary database using the LogXptStatus monitorable database property. If redo transport services have an error, then use the error message to determine further checking and resolution action. For example:

  • If the error indicates the standby database is not available, you need to restart the standby database.

  • If the error indicates no listener, you need to restart the listener.

  • If the error indicates the standby database has no local destination, you need to set up a standby location to store archived redo log files from the primary database.

9.2.3 Many Log Files Are Received on a Standby Database But Not Applied

By viewing the Performance page or Log File Details page in Enterprise Manager, you have determined that the standby database accumulates too many log files without applying them.

Solution There are many possible reasons why archived redo log files might not be applied to the standby database. Investigate why the log files are building up and rule out the valid reasons.

If the current status of the standby database is not normal:

• Determine whether or not the log apply services might be unexpectedly stopped. See the ORA-16766 (for physical standby databases) or ORA-16768 (for logical standby databases) error description and solution statement for more help.

• If this is a logical standby database, check to see if a failed transaction has occurred.

• If you want to suppress the error while you investigate the problem, you can temporarily disable broker management of the database.

  See Also:

  Chapter 7 for additional information about disabling the database using the DGMGRL command-line interface

If the current status of the standby database is normal:

• Verify the state of the standby database is APPLY-ON (not in the APPLY-OFF state).

• Verify the state of the primary database is TRANSPORT-ON (not in the TRANSPORT-OFF state).

  See Also:

  Chapter 8 for additional information about the LogShipping database property

• Check to see if log files are building up because the value of the DelayMins property is set too large. (Log apply services will delay applying the archived redo log files on the standby database for the number of minutes specified.)

  See Also:

  Chapter 8 for additional information about the DelayMins database property

• If you cannot see any errors, compare the archive rate to the apply rate on the Performance page in Enterprise Manager to see if the apply rate is lower than the archive rate.

9.2.4 The Request Timed Out or Enterprise Manager Performance Is Sluggish

If the broker requests are not completing within the normal timeout parameters, try the following actions to solve the problem:

1. Verify the network is operating appropriately.

2. Try to ping all of the nodes in the configuration.

3. Try reconnecting through another database to retry the operation.

4. Run the VERIFY command to determine on which database the broker is unable to process the requests.

9.2.5 The Primary Database is Flashed Back

If the primary database is flashed back, the standby databases in the configuration must be also be flashed back or re-created to be viable targets for switchovers or failovers. The broker will report errors for the standby databases if the primary database has been flashed back.

For more information about restoring the viability of a standby database that was disabled by the broker, see Section 5.4.3.

9.2.6 Standby Fails to Automatically Start Up Due to Unknown Service (ORA-12514)

If the DGMGRL CLI fails to automatically start up an instance after a broker operation (for example, a switchover, reinstatement, convert to physical standby, or upgrade of protection mode to maximum protection mode), and you receive an ORA-12514: TNS:listener does not currently know of service requested in connect descriptor error, then you must manually start the instance to complete or continue the broker operation.

You can restart the instance before or after completing the following steps:

1. Issue the following DGMGRL CLI command to check the value of the StaticConnectIdentifer configurable property for the instance the DGMGRL CLI was unable to restart. (You will have to connect to another running instance to issue this command):

   DGMGRL> SHOW INSTANCE VERBOSE 'instance_name' ON DATABASE db_unique_name;
   

2. The static service name specified in the value of the StaticConnectIdentifer instance property should be registered with the listener specified in the property value. The default value for the static service name is of the following form:

   db_unique_name_DGMGRL.db_domain
   

   See Section 2.2 for more information about this, and other prerequisites, for using the broker.

3. Confirm that the static service name is registered with the listener specified in the StaticConnectIdentifer configurable property value by using the Listener Control utility's status command. If the static service name is properly registered with the listener, it will be included in the output generated by the following command:

   lsnrctl status
   

4. If you are working in an Oracle RAC environment, you may want to repeat steps 1 and 2 for each instance to ensure that a static service name is properly registered with its respective listener.

9.3.1 Failed Switchovers to Physical Standby Databases

Examine the alert and DRC log files on the original primary and the target standby databases to determine the cause of the failure. The following sections describe the steps necessary to recover from a failed switchover to a physical standby, based on the types of errors contained in the log files:

• Failure to Convert the Original Primary Database

• Failure to Convert Target Physical Standby Database

• Failure to Open New Primary Database

9.3.2 Failed Switchovers to Logical Standby Databases

Examine the alert and DRC log files on the original primary and the target standby databases to determine the cause of the failure. The following sections describe the steps necessary to recover from a failed switchover to a logical standby, based on the types of errors contained in the log files:

• Failure to Convert Original Primary Database

• Failure to Convert Target Logical Standby Database

9.3.3 Additional Problems That May Occur During a Switchover Operation

Problem: The broker switchover fails due to problems with redo transport services.

Solution:  Verify the state and status of the primary and standby database by viewing its information on the Enterprise Manager Data Guard Overview page or through the DGMGRL client SHOW DATABASE commands.

If using Enterprise Manager, then run the Verify operation after the switchover completes to examine the alert log file of the new primary database and to verify the status of the configuration.

Problem: The switchover may fail during verification checks done by Data Guard broker (for example, redo transport services might return errors on a database that is involved in the switchover).

Solution: Choose another database for the switchover or fix the problem by transporting the archived redo log files.

9.4.1 Failed Failovers to Physical Standby Databases

Use the steps below to recover from a failed broker failover to a physical standby database.

9.4.2 Failed Failovers to Logical Standby Databases

1. Examine the alert and DRC log files on the target standby database to determine the cause of the failure and correct the problem.

2. Connect to the target standby database and disable fast-start failover using the FORCE option if it is enabled.

3. Retry the broker failover.

4. Reinstate the old primary database. All bystander standby databases will be re-created from a copy of the new primary database.

5. Reenable fast-start failover if it was disabled in step 1.

If broker failover continues to fail, you should stop the broker on all databases in the Data Guard configuration (set the DG_BROKER_START initialization parameter to FALSE). Remove the Data Guard broker configuration files from all databases. Attempt a manual failover using the guidelines for role transitions in Oracle Data Guard Concepts and Administration.

9.5.1 Problems Starting the Observer

Only one observer can be observing the broker configuration at any given time. If you attempt to start a second observer, one of the following errors is returned:

ORA-16647: could not start more than one observer
DGM-16954: Unable to open and lock the Observer configuration file

Use the DGMGRL SHOW CONFIGURATION VERBOSE command to determine the location of the observer that is currently associated with the broker configuration.

DGMGRL> SHOW CONFIGURATION VERBOSE;
 
Configuration - DRSolution
 
  Protection Mode: MaxAvailability
  Databases:
    North_Sales  - Primary database
    South_Sales  - (*) Physical standby database
 
  (*) Fast-Start Failover target
 
  Properties:
    FastStartFailoverThreshold      = '60'
    OperationTimeout                = '30'
    FastStartFailoverLagLimit       = '30'
    CommunicationTimeout            = '180'
    FastStartFailoverAutoReinstate  = 'TRUE'
    FastStartFailoverPmyShutdown    = 'TRUE'
    BystandersFollowRoleChange      = 'ALL'
 
Fast-Start Failover: ENABLED
 
  Threshold:        180 seconds
  Target:           South_Sales
  Observer:         observer.example.com
  Lag Limit:        30 seconds (not in use)
  Shutdown Primary: TRUE
  Auto-reinstate:   TRUE
 
Configuration Status:
SUCCESS

9.5.2 Problems Because the Observer Has Stopped

If the observer host machine crashes, the broker configuration is no longer observed and fast-start failover is no longer possible. In this case, you may have to move the observer to a new host if the original host machine cannot be repaired in a timely fashion. To move the observer, you must stop allowing the first observer to observe this broker configuration, and then start a new observer on another host.

1. Issue the DGMGRL STOP OBSERVER command to sever the link between the original observer and the broker configuration:

   DGMGRL> STOP OBSERVER;
   Done.
   

2. Issue the DGMGRL SHOW CONFIGURATION VERBOSE command to verify that the configuration is no longer being observed:

   DGMGRL> SHOW CONFIGURATION VERBOSE;
    
   Configuration - DRSolution
    
     Protection Mode: MaxAvailability
     Databases:
       North_Sales  - Primary database
       South_Sales  - (*) Physical standby database
    
     (*) Fast-Start Failover target
    
     Properties:
       FastStartFailoverThreshold      = '60'
       OperationTimeout                = '30'
       FastStartFailoverLagLimit       = '30'
       CommunicationTimeout            = '180'
       FastStartFailoverAutoReinstate  = 'TRUE'
       FastStartFailoverPmyShutdown    = 'TRUE'
       BystandersFollowRoleChange      = 'ALL'
    
   Fast-Start Failover: ENABLED
    
     Threshold:        180 seconds
     Target:           South_Sales
     Observer:         (none)
     Lag Limit:        30 seconds (not in use)
     Shutdown Primary: TRUE
     Auto-reinstate:   TRUE
    
   Configuration Status:
   SUCCESS
   

3. Note that you do not need to issue the DGMGRL SHOW CONFIGURATION command to verify that the observer has actually stopped. Successful completion of the DGMGRL STOP OBSERVER command will allow a new observer to become associated with the configuration.

9.5.3 Capturing Observer Actions in the Observer Log File

You can use the DGMGRL -logfile option to start the observer, so that all of the troubleshooting actions performed in Section 9.5.1 can be captured in a file. For example:

% dgmgrl -logfile observer.log / "start observer"

All the observer output is then recorded in a file named observer.log in the current working directory where you issued the DGMGRL command. If the specified log file is not accessible, then the observer output is sent to standard output as though a log file had not been specified.

Note that this is not only useful for troubleshooting problems with the observer, but also for troubleshooting problems with fast-start failover in general.