data guard failover steps

They may be reinstated if Flashback Database is enabled on those databases. You can disable fast-start failover if necessary, by using the FORCE option. Before stopping an observer, note the following: The observer does not stop immediately when you issue the STOP OBSERVER command. So if the original Primary database is still accessible, you should always consider a switchover first. If the standby database is not enabled for management by the broker, then the failover cannot occur. At this point, you can either: Disable fast-start failover (described in Disabling Fast-Start Failover) and attempt to open the former primary database, Manually reinstate the former primary database, as described in Reenabling Disabled Databases After a Role Change. If it detects that Flashback Database was disabled, either manually, or automatically because Flashback Database discovered a problem, Broker signals "ORA-16827: Flashback Database is disabled". If fast-start failover is enabled and the Datafile Write Errors condition is specified, then a fast-start failover is initiated if write errors are encountered in any data files, including temp files, system data files, and undo files. As mentioned above, Maximum Availability mode is mandatory for Oracle Database 10g and optional for Oracle Database 11g. FastStartFailoverLagLimit property. Make sure the last redo data transmitted from the Primary database was applied on the standby database. Failover automation ensures a seamless transition from the primary database to a synchronized standby database in cases of failure, while ensuring database availability by replaying uncommitted in-flight transactions. Note that this does not guarantee no data will be lost. The observer is the key element that separates Data Guard failover from its pre-FSFO role as the plan of last resort to its leading role in a robust high availability solution. ASYNC. first recording that a fast-start failover cannot happen. All standbys other than the failover target are considered bystanders (v$database.fs_failover_status = 'BYSTANDER'). database that has the least amount of unapplied redo (smallest apply lag). A switchover guarantees no data loss and is typically done for planned maintenance of the primary system. This is the recommended method for disabling fast-start failover. Stores the observer runtime data file and observer configuration file in The observer immediately initiates a fast-start failover, as long as the failover target database is in a valid fast-start failover state ("observed" and either "synchronized" or "within lag") to accept a failover. If the specified log file is not accessible, or the LOGFILE IS option is not used, then the observer output is sent to standard output. The following conditions apply when multiple observers are registered for one configuration: When fast-start failover is enabled, one of the observers is the master observer. Starting the Observer Using Cloud Control. For example: In the following example, assume the network between the primary database and the observer has failed. All other registered observers are considered to be backup observers. If the designated fast-start failover target develops a problem and cannot be the target of a failover, then the broker automatically changes the fast-start failover target to one of the other candidate targets. As described in theFlashback Database section, Flashback Database takes place in two stages: a restore stage and a media recovery stage. Automatic failover quickly and reliably fails over the standby Autonomous database to the primary database role, without requiring you to perform any manual steps. The default name of the observer runtime data file is Reenabling Disabled Databases After a Role Change describes how to restore their viability as standby databases. The broker verifies the state and status of the databases to ensure that the switchover transitioned the databases to their new role correctly. This prevents a "split brain" condition if a failover occurs since none of the changes made to the isolated primary can be made permanent. An application should use caution when calling the DBMS_DG.INITIATE_FS_FAILOVER function because the observer will initiate failover, if at all possible. If fast-start failover is already enabled, the If local_listener is already in use, add the Data Guard listener to the list. The broker reinstates bystander standby databases that were disabled during a failover as standby databases to the new primary database. This list contains some recommendations to obtain better performance when using fast-start failover. STOP OBSERVING [cfg_group_name] stops LOCAL observers running on this host (where this DGMGRL is running) for all broker configurations in a specified group. Running a StatusReport on the primary should verify that the error is due to a missing observer. https://www.facebook.com/dbahariprasath/? The observer is perfectly satisfied if all of the redo it needs to meet your durability requirements has been received by the failover target. If Flashback Database history is insufficient, the observer will not be able to reinstate and you will have to manually reinstate from backup or by primary duplication. The example uses 10 seconds. This is normal. Most in-progress failures cannot be restarted (for example, archived redo log file corruption on the primary database). See Enabling Fast-Start Failover for more information. If the failover target is a logical standby database, the original primary database and all physical and snapshot standby databases in the configuration will be disabled. Configure the TNSNAMES.ORA file on the observer system so that the observer is able to connect to the primary database and to the pre-selected target standby database. Switch-over steps: Step-A: Shutdown primary database: SQL> shut immediate; Database closed. Improper Oracle Net configuration is a leading cause of reported FSFO issues. Issue the following SRVCTL commands: Now the correct services are running on the correct databases. If there are multiple observers, then only one of them is the master observer. See Oracle Data Guard Concepts and Administration for information about tuning the log apply rate for a physical standby database. After FSFO is enabled, Broker will continue to check that Flashback Database is enabled during health checks. Application Continuity is an Oracle Database feature that enables rapid and nondisruptive replays of requests against the database after a recoverable error that made the database session unavailable. In an Oracle Data Guard configuration, the SRVCTL -startoption and -role are updated after switchover to reflect the current open mode and database role on the new primary and standby databases. Open another prompt and connect to SQLPLUS: On Windows, the directory specified by the DG_ADMIN With FSFO enabled, Broker expects to find an observer, which we haven't started yet, so if you verify the at this point with 'show configuration', Broker will report a warning (if it doesn't, give it a minute to discover that the observer isn't there). Displays only on the target standby database when it is SYNCHRONIZED with or is TARGET UNDER LAG LIMIT of the primary database, has connectivity to the observer, but the primary database does not have a connection to the observer. For a system to process an instruction involving data access, these are the certain steps involved: Fetch the block of data from the hard disk (secondary/permanent storage) to the primary memory (e.g. Figure 6-2 The Observer in the Fast-Start Failover Environment. In case of worst situation with data guard primary database, or not available for production than we can activated standby database as a primary production database. This property also affects whether the broker skips viability checks of bystander standby databases when a fast-start failover occurs. STANDBY>connect /@STAN as sysdba In order to apply redo data to the standby database as soon as it is received, use Real-time apply. Change Standby to Primary Database. Use Cloud Control or DGMGRL to perform either a complete (recommended) or an immediate failover. VALIDATE This document describes how to setup clients to connect to Data Guard databases (primary and standby) and configure automatic client failover such that in case there is role change due to switchover or . To stop the observer when fast-start failover is enabled, the primary database and target standby database must be connected and communicating with each other. commands. directory. Steps that require the primary to be in a mounted (not open) state are grouped together in the section below entitled Steps Requiring a Bounce of the Primary. When a fast-start failover occurs because either a user configurable fast-start failover condition is detected or an application initiates a fast-start failover by calling the DBMS_DG.INITIATE_FS_FAILOVER function, the former primary database is always shut down and never automatically reinstated. The FS_FAILOVER_STATUS column in the V$DATABASE view for the target standby database displays a reason why fast-start failover cannot occur. To reenable broker management of these databases, you must reinstate or re-create the databases using one of the following procedures: If a database can be reinstated, the database will show the following status: Reinstate the database using the DGMGRL REINSTATE DATABASE command or the reinstate option in Cloud Control, as described in How to Reinstate a Database. The required attributes vary depending on your configuration (including whether your environment is Oracle RAC-based or single-instance). It will return PRIMARY, If a single-instance primary database (either Oracle RAC or non-Oracle RAC), or if all instances of an Oracle RAC primary database fail, the observer attempts a fast-start failover. Tailing the alert logs on the primary and standby is a good way to watch Broker in action and get familiar with how it performs various tasks. We'll leave the other properties at their default values for the walkthrough, but you should become familiar with all of the Broker config and database properties. usually within three seconds if fast-start failover is enabled. A failover is a role transition in which one of the standby databases is transitioned to the primary role after the primary database (all instances in the case of an Oracle RAC database) fails or has become unreachable. Most of the network services used in a FSFO environment may use dynamic registration, but to enable Broker to restart instances during role transitions or during reinstatement after a failover, you must define a static service named db_unique_name_dgmgrl. This feature enables RMAN to duplicate an existing database over the network without requiring a backup to disk or tape. SHOW OBSERVERS [FOR fg_group_name ] shows information about observers for all configurations in the specified group. Transitions the target standby database into the primary database role, as follows: Changes the role of the database from standby to primary. If you are performing an immediate failover, then the database role is changed to primary without applying any accumulated redo data. This section lists the steps the master observer takes to determine if a fast-start failover is needed and then to perform one, if necessary. Contains the observer runtime data file for the broker Es gratis registrarse y presentar tus propuestas laborales. This document only talks about switchover involving physical standby database. Displays if the standby database's redo applied point does not lag the primary database's redo generation point by more than the number of seconds specified by the FastStartFailoverLagLimit configuration property and the configuration is operating in maximum performance mode. An immediate failover is the fastest type of failover. FSFO builds upon a number of other Oracle technologies and features such as Data Guard, Flashback Database, and Data Guard Broker. observer, whether it is currently connected to the primary and target standby databases, Let's run the command on the primary database to validate if the environments are ready for the role transition : JITPRD> alter database switchover to JITSDB verify; alter database switchover to JITSDB verify * ERROR at line 1: ORA-16475: succeeded with warnings, check alert log for more details Note that these properties only affect whether primary shutdown and automatic reinstatement are performed if a fast-start failover occurs because the primary crashed or was isolated from the observer and target standby database. 1,000,000 block changes on a small set of blocks generates less Flashback Database history than 1,000,000 changes on a larger set of blocks. If you intend to switch back to the original primary database relatively soon, you may allow the physical and snapshot standbys to remain disabled. required permissions, DGMGRL reports an error. An existing connection which is already closed from the database side would throw an error. If the observer is unable to regain a connection to the primary database within the specified time, then the observer begins a fast-start failover provided the standby database is ready to fail over. See "Database Service Configuration Requirements" for additional information about how the broker interacts with Oracle Restart. If a group name is not specified, then SHOW OBSERVERS alone is also a valid command. This walkthrough uses Maximum Availability mode to achieve "zero data loss". command is submitted successfully, the command-line prompt on the You will then need to re-create the physical standby databases from a copy of the new primary database before you can reenable them. Refer to the appropriate Oracle RAC or Oracle Restart documentation for further information. Stop the observer using the DGMGRL STOP OBSERVER command. Manual failover to the fast-start failover target can be performed without receiving an acknowledgement from the observer. In a Managed Instance with multiple databases in Azure we can have high availability. Once you have completed the switchover back to the original primary, you may then reenable the physical and snapshot standby databases since they are still viable standbys for the original primary database. The failover was to a logical standby database. A failed ping is a ping to Figure 6-1 shows the relationships between the primary database, target standby database, and observer during fast-start failover: Before Fast-Start Failover: Oracle Data Guard is operating in a steady state, with the primary database transmitting redo data to the target standby database and the observer monitoring the state of the entire configuration. When fast-start failover is enabled, the primary and standby randomly choose one of the registered observers to be the master. Displays when the target standby database does not have all of the primary database redo data and the configuration is operating in maximum availability mode. See Directing a Fast-Start Failover From an Application). Oracle Database 11g observers are incompatible with 10g databases and vice-versa. If the primary or target standby databases lose connections to all backup observers, then the broker does not try to nominate a backup observer as the new master observer, and the broker reports that the configuration is not observed. Observer uses the value of the DGConnectIdentifier property to connect to and monitor the primary and target standby databases. failover configuration file, this script is run. After the database has been re-created, enable broker management of the re-created standby database by using the DGMGRL ENABLE DATABASE command. (Note that the target standby cannot be a far-sync instance. PRIM> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN; Broker keeps its configuration details in flat file. Failover:- In case of worst situation with data guard primary database, or not available for production than we can activated standby database as a primary production database. present, you must start the observer manually using the following This lets you take advantage of the broker's Reconnect within the time specified by the FastStartFailoverThreshold property. If it exists, and it contains a pre-callout script location, This file is stored in the To verify the observer is started and the configuration is ready for The ObserverOverride configuration property, when set to TRUE, allows an automatic failover to occur when the observer has lost connectivity to the primary, even if the standby has a healthy connection to the primary.

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