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If it's not, DGB will not allow the failover to continue until the DBA has manually resolved any discrepancies. If the target is a snapshot standby database, the broker first converts the database to a physical standby database. If a fast-start failover was initiated because the primary database had crashed or lost connectivity with the master observer and target standby database, then the master observer automatically attempts to reinstate the former primary database as a standby database, if the FastStartFailoverAutoReinstate configuration property is set to TRUE. milliseconds and that of ObserverRetryCount is 10. select name,open_mode,database_role from v$database; Note: first recording that a fast-start failover cannot happen. This is typically done for planned maintenance of the primary system. This can be avoided by first disabling fast-start failover with the FORCE option on the target standby. The observer maintains state information in a file. Note: if the observer loses contact with the primary, but the standby does not, the observer can determine that the primary is still up via the standby. Using Shared Server (MTS) or connection pooling can result in unpredictable behavior. However, you can change the name or the location of the file if you start the observer using the DGMGRL START OBSERVER command and include the FILE IS qualifier. The real test of the configuration is a successful role transition in both directions with both switchover and FSFO failover. (Note: 11.1.0.7 adds the StaticConnectIdentifier Broker database property to allow you to specify a different service name.) Oracle Database 10g allows a different password file to be used as long as the SYS passwords are the same on the primary and standby. Read-Only Standby and Active Data Guard If you are performing an immediate failover, then the database role is changed to primary without applying any accumulated redo data. If clients are already configured to automatically time out and reconnect if they don't get a response from the database, a simple but effective approach is to use a network alias (e.g. The services include switchover, switchback and failover. contains important information about the observer. Use Cloud Control or DGMGRL to perform either a complete (recommended) or an immediate failover. The new ConfigurationWideServiceName configuration property can be used to simplify setting up this connect identifier. Logical standby databases that are disabled during failover can be reinstated. This prevents a "split brain" condition if a failover occurs since none of the changes made to the isolated primary can be made permanent. You can manually stop a specific observer or all observers. Oracle Data Guard is a solution provider to businesses by offering data protection and its disaster recovery along with its high availability. See Reenabling Disabled Databases After a Role Change. See the START OBSERVER command for more information. An immediate failover is the fastest type of failover. FastStartFailoverLagLimit configuration property is set to zero) or For reliable startup, the initial connection should always be made to the primary. 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. If you have not used the SET ObserverConfigFile command after starting the current DGMGRL client, then the result will always be: ObserverConfigFile=observer.ora. property. If you cannot tolerate any loss of data, then ensure that the configuration protection mode is set to maximum availability or maximum protection. Observer sites monitor the fast-start failover environment. You can enable fast-start failover from any site while connected to any database in the broker configuration. The following sections describe how to perform manual failovers: Reenabling Disabled Databases After a Role Change. That is, if the observer is connected to any instance in the Oracle RAC, all instances will show a value of YES. Oracle Data Guard configuration with DGMGRL. Otherwise, the DUPLICATE TARGET DATABASE command will fail with "RMAN-20208: UNTIL CHANGE is before RESETLOGS change". the location of the observer log file, and the location of the observer runtime data observer_hostname.log. Broker will validate the configuration, set parameters on both databases, and start managed recovery. restart the new physical standby database. Data Guard Broker - Controls the creation and monitoring of Data Guard. The broker disables all of the physical and snapshot standby databases in the configuration. Follow Smart way of Technology on WordPress.com. What is true about Data Guard setup with fast-start failover? Theoretically, this method can be used when a data guard failover occurred between the primary and standby database, but not a switchover. On Windows, the directory specified by the DG_ADMIN This can be avoided by first disabling fast-start failover with the FORCE option on the target standby. It is possible to manually perform a completer failover to a standby database that receives redo data from a far sync instance. The primary database, it attempts to disable fast-start failover on as many databases in the configuration with which it has a network connection. Overall commit latency is increased by the round-trip network latency. groups used by multiple configuration commands. 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. fast-start failover to the target standby database if conditions warrant a failover. If a database must be re-created from a copy of the new primary database, it will have the following status: Re-create the standby database from a copy of the primary database and then reenable it, as described in How to Re-create and Reenable a Disabled Database. However, re-enabling Flashback Database will require a bounce since the database must be mounted and not open. This section describes how to configure and verify each prerequisite. fast-start failover has not occurred to the target standby database. Note: the FSFO observer version must match the database version. If Flashback Database was enabled on the primary database.If not, the whole setup process must be followed, but this time using the original primary server as the standby. If you don't already have a Flash Recovery Area (FRA), you will need to create one for Flashback Database. The original primary database can now be configured as a standby. This specifies how often the observer establishes a new connection to the primary database. Figure 6-2 shows the observer monitoring a fast-start failover configuration. Log in as a test user and make some changes that won't impact other parts of the system. Bystander standby databases that are not disabled by the broker after the switchover will continue operating in the state they were in before the switchover. Note that the new primary database does not need to be restarted. If there is only one registered observer, then it works in the same manner that a single observer worked prior to the advent of multiple observers in Oracle Database 12c Release 2 (12.2.0.1). Click Failover. When fast-start failover is enabled, the primary and standby randomly choose one of the registered observers to be the master. Goal. See the START OBSERVER 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. If both HVR and Data Guard were running without latency or if no changes were made to the source database at the time of the failover, it can be assumed that all databases are synced and the no extra steps are necessary; the steps for Graceful Failover can be followed. The former primary database is disabled. POTENTIAL DATA LOSS: Fast-start failover is enabled with some data loss. This list describes restrictions when fast-start failover is enabled. environment variable is set and the specified directory has the Configure the protection mode. See Sources of Diagnostic Information for details about the broker's drc* log files. An observer can be moved from one computer to another through a process of stopping it on one system and and re-starting it on another. alter database recover managed standby database finish; alter database activate standby database; Managed recovery process has been stopped between primary and standby database and standby becomes primary database. This is because the -role qualifier is taken into account only by Data Guard broker, and at database startup. It will return PHYSICAL STANDBY, same permissions. Commit latency is not affected by redo transfer, but committed transactions whose redo has not been received by the standby will be lost during failover. The RedoRoutes property on the primary if the new value would result in the primary not being able to ship redo to the current fast-start failover target standby. Broker stores it configuration information in a mirrored set of files outside the database. Please contact us at contactus@smarttechways.com. primary. Services that must be active in any given database role (primary, physical standby, logical standby, or snapshot standby) must be configured with the Server Control utility (SRVCTL) explicitly on each database where the service must be active. You can use the SHOW CONFIGURATION WHEN PRIMARY IS command to show the redo transport configuration (based on each member's setting of the RedoRoutes property) that would be in effect if the specified database were the primary database. have received all the redo data the primary has generated in order for automatic failover to operation. To avoid the overhead of recording every change to every block, Flashback Database takes a "fuzzy" snapshot every 30 minutes and only records the before-image block upon its first change since the last snapshot. Create or update the fast-start failover callout configuration file and include STAN is now transitioned to the primary database role.Now your PHYSICAL STANDBY Database has become PRIMARY. The database on which the procedure is called notifies the observer. They may be reinstated if Flashback Database is enabled on those databases. To start an immediate failover, use the DGMGRL FAILOVER TO database-name IMMEDIATE command. Broker Configuration Has Only One Registered Observer. In maximum protection mode, set the LogXptMode database property to SYNC (note that in maximum protection mode, a far sync instance cannot be used to ship redo to a standby). These are the actions the broker performs after you start a complete failover. Failovers become routine. Without the credentials, Broker will complete the role transition, but will leave the databases in need of a manual restart. The broker selects a target based on the order in which they are specified on the FaststartFailoverTarget property. It is instructive to watch the alert logs on both databases as well as the observer log after aborting the primary to gain insight into what happens during FSFO failover. To override this behavior and allow a fast-start failover to occur if the observer is unable to contact the primary for more than FastStartFailoverThreshold seconds, set the ObserverOverride property to TRUE. If this operation is successful, a zero data loss failover may be possible even if the primary database is not in a zero data loss protection mode. So SALESRW will start on CHICAGO (which is now the primary) and SALESRO will start on BOSTON (which is now the physical standby). This file contains connect identifiers to both the primary and the target standby databases. After the fast-start failover completes successfully, the master observer will attempt to reinstate the former primary database as a new standby database when a connection to the former primary database is reestablished, and the FastStartFailoverAutoReinstate configuration property is set to TRUE. A good method to determine Flashback Database storage requirements is to enable Flashback Database and observe the amount of storage it uses during several peak loads. In this example, there are 3 ORLs with a max group# of 3. Restore - Flashback Database restores the datafiles to the closest snapshot prior to the specified SCN. The values that indicate FSFO is ready for failover are listed below. Keep this trigger as simple and reliable as possible, limiting it to only what is absolutely necessary at the moment of role transition, since any failures at this point may affect availability. If the database is not enabled, you will not be able to perform a failover to this database. You can customize fast-start failover setup for a specific application by using the DBMS_DG PL/SQL package. SQL>connect /@STAN as sysdba If a non-zero value is specified for the See the Cloud Control online help for more information. It is not reversible. The ObserverOverride and ObserverReconnect properties allow you additional control over the connection to the primary. Credentials Required for Access to Broker Configurations. directory specified by this variable does not exist, or the directory does not have the The The most common problems are mismatched Data Guard protection modes and LogXptMode properties and forgetting to enable Flashback Database on the primary or standby. Use the FastStartFailoverTarget configuration property on the current primary database to specify one or more fast-start failover targets. A far sync instance or Zero Data Loss Recovery Appliance is not a database and therefore cannot be the target of a role transition. The configuration and database status report the same error messages as are returned when there is only one registered observer. Whenever possible, you should switch over to a physical standby database: If the switchover transitions a physical standby database to the primary role, then: The original primary database will be switched to a physical standby role. 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. For example, if the limit specified is 30 seconds (the default), FSFO guarantees that all transactions that committed prior to 30 seconds ago are preserved during failover. RAM). It is possible to manually perform an immediate failover to a standby database that receives redo data from a far sync instance. To stop the observer when fast-start failover is disabled, the primary database must be running. When the standby becomes available again, the primary and standby re-synchronize and resume synchronous redo transfer. When you run commands that need access to the observer Don't initiate failover unless at least 30 minutes of history is available. Now it will return PRIMARY. The services required on the primary database are: Log Writer Process (LGWR) - Collects redo information and updates the online redo logs. To start the observer with DGMGRL, issue the following You can, however, perform a manual failover to a snapshot standby. Starting Observers as Background Processes. If the Broker configuration is changed to make a bystander the new failover target (probably a good idea if the failed database will be down for a while), the observer will not automatically reinstate the former primary because it is no longer part of the FSFO configuration. Once an observer is started, no further user interaction is required. Flashing back a database occurs in two stages: For FSFO environments, set db_flashback_retention_target = 60 or higher to provide sufficient Flashback Database history for automatic standby reinstatement. It uses the connect identifier specified in the observer configuration file to locate the credentials for a broker configuration from the Oracle wallet. The string "NONAME" cannot be used as an observer name. Default value is 100 ConfigurationSimpleName represents A fast-start failover occurred because a user-configurable condition was detected or was requested by an application by calling the DBMS_DG.INITIATE_FS_FAILOVER function. Note that enabling FSFO does not make the configuration ready for automatic failover - that requires an observer, which we'll get to next. Facebook:https://www.facebook.com/HariPrasathdba You can also specify a list of ORA- errors that will initiate FSFO failover. In such a case, no attempt is made to transmit any unsent redo from the cascader to the terminal standby. This walkthrough assumes that all ORLs and SRLs on the primary and standby databases are the same size. The application needs to catch this error and respond accordingly. Note that the FastStartFailoverThreshold property can be changed even when fast-start failover is enabled. The default name for If only a path is specified, the files are The column value for V$DATABASE.FS_FAILOVER_STATUS will be SYNCHRONIZED in a configuration operating in maximum availability mode, and it will be TARGET UNDER LAG LIMIT in a configuration operating in maximum performance mode when ready to fast-start failover. Reinstatement is supported only after failover in a broker configuration. Stops Redo Apply or SQL Apply on the standby database immediately, without waiting until all available redo data has been applied. Make sure the last redo data transmitted from the Primary database was applied on the standby database. Example 6-2 Sample Observer Configuration File. If you already have an FRA, you may need to increase its size in order to accommodate the Flashback Database files. The following is an example of querying the V$FS_FAILOVER_STATS view: Disabling fast-start failover prevents the observer from initiating a failover to the target standby database. We'll start with switchovers. Oracle Database 11g FSFO adds support for Maximum Performance mode (async redo transfer), providing the flexibility to trade durability for performance. For this build, we will use a single physical standby database. Provides an automatic failover environment $DG_ADMIN/config_ConfigurationSimpleName/callout In Oracle Database 11g, the password file on the standby must be a physical copy of the password file on the primary due to security enhancements introduced in Oracle Database 11g. You might, for instance, use this to allow the observer to monitor the databases using the same connect identifiers as the client applications. files include the observer configuration file (observer.ora), observer log The playground: In the following example, ObserverReconnect is set to 30 seconds. ObserverConfigFile is a DGMGRL session runtime property. Set this property for the primary and target standby database if you want the observer to use a different connect identifier than that used to ship redo data (that is, the connect identifier specified by the DGConnectIdentifier property). instructions for the DGMGRL command-line interface. This example shows the verbose mode of the 'show configuration' command that provides FSFO-specific information. Duplicate configuration names in configuration definitions are not allowed. Oracle Database 11g adds the ObserverConnectIdentifier database property to the Broker configuration, allowing you to specify a connect identifier for the observer to use for monitoring the primary and failover target. In a Data Guard environment primary database is open in read write mode and the standby database in read only mode for reporting purpose. Fast-Start Failover in Oracle 11g Data Guard. Make sure that xdpyinfo exist under PATH variable. The physical and snapshot standby databases will have to be re-created from a copy of the new primary database. Verify there are no active users connected to the databases. Switchover Steps. lower detection times for primary database failures, you must client-side broker files, the specified values are used. The SHOW CONFIGURATION command will show you which databases can be reinstated and which databases must be re-created. orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID. Verify the target standby database is ready for failover. A complete failover also attempts to avoid disabling any standby databases that were not the target of the failover, so that they may continue serving as standby databases to the new primary database. For example: The following example shows the fast-start failover information for the DRSolution configuration: The following SHOW OBSERVER command displays information about multiple observers in the DRSolution broker configuration.
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