data guard failover steps

This list contains some recommendations to obtain better performance when using fast-start failover. Set the FastStartFailoverThreshold property to specify the number of seconds you want the observer and target standby database to wait (after detecting the primary database is unavailable) before initiating a failover. During failover, bystanders "follow" the primary by default, flashing back and reapplying redo from the new primary as necessary. Contains the observer runtime data file for the broker Use the Cloud Control Fast-Start Failover wizard or the DGMGRL ENABLE FAST_START FAILOVER command to enable fast-start failover. Displays if the standby database's redo applied point lags 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. Presetting database properties related to redo transport services, such as LogXptMode, NetTimeout, StandbyArchiveLocation, StandbyAlternateLocation, and RedoRoutes. Once you set these properties, their values persist through role changes during switchover and failover. Do not attempt to reinstate the old primary database if an ORA-752 or ORA-600 [3020] error has occurred at the failover target. In these sample commands, the ellipse () signifies any other add service options you wish to supply. 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). Use the FastStartFailoverTarget configuration property on the current primary database to specify one or more fast-start failover targets. Displays on the primary database after loss of connectivity to the target standby database and the change to the UNSYNCHRONIZED state (maximum availability mode) or to the TARGET OVER LAG LIMIT state (maximum performance mode) cannot be confirmed by either the target standby database or the observer. irrespective of its content, indicates that the script executed successfully. REINSTATE REQUIRED is present only after fast-start failover has occurred and shows on both the new primary database and the database undergoing reinstatement. Data Guard Broker - Controls the creation and monitoring of Data Guard. 3. status before the crash. See Manual Failover for complete information about manual failovers. The reinstated database acts as the fast-start failover target for the new primary database, making a subsequent fast-start failover possible. Provides an automatic failover To see Manual Switch Over Manual SwitchOver in Oracle To see Manual Fail Over Manual Failover in Data Guard With Oracle Data Guard [] What is true about data guard set up with fast-start failover (FSFO) in Oracle Cloud Infrastructure (OCI)? maximum availability and maximum performance modes, to avoid a Oracle Data Guard Broker is a utility that can help you manage your Oracle Data Guard. When this property is set to NONE, the broker will disable all bystander standby databases without checking whether they have applied more redo data than the new primary database. The default name of the observer runtime data file is Figure 6-2 shows the observer monitoring a fast-start failover configuration. North_Sales is in the primary role. 3. Bounce your database and verify database name its open mode and its role: SQL> shutdown immediate; ORA-01109: database not open Database dismounted. If failover is not possible for some reason, then the master observer will continue checking whether the standby database is ready to fail over. You must specify it every time you start a new DGMGRL client. Configure one or more active standby databases Minimize downtime for upgrades Fast-Start Failover allows Data Guard to automatically failover to a previously chosen standby database without requiring manual intervention to invoke the failover. Permissions Required by the DG_ADMIN Directory. Thus, the command-line prompt on the observer computer does not The minimum detection time is 6 seconds, which is the default It automatically recovers the maximum amount of redo data for the protection mode the configuration is operating in. The group of broker configurations to be managed is declared in the observer configuration file. directory specified by this variable does not exist, or the directory does not have the Client-side broker Overview of Switchover and Failover in a Broker Environment. By default, the observer will initiate failover to the target standby if and only if ALL of the following are true: Oracle Database 11g Rel 1 introduced user configurable failover conditions that can trigger the observer to initiate failover immediately. To run an observer as a background process, use the DGMGRL command START OBSERVER IN BACKGROUND. Just be sure to include a Flashback Database history check in the script to provide an option to abort if a failover would require a manual reinstate. Disabling Fast-Start Failover Using DGMGRL. In this case, the FS_FAILOVER_STATUS and FS_FAILOVER_OBSERVER_PRESENT columns will appear as shown in the following table and fast-start failover will not occur: Oracle Database Reference for more information about the V$DATABASE view. The following sections describe how to perform manual failovers: Reenabling Disabled Databases After a Role Change. 1. The example below takes advantage of the 11g RMAN Active Database Duplication feature. database. Provides an automatic failover environment Fast-start failover can be used only in a broker configuration and can be configured only through DGMGRL or Cloud Control. The act of switching roles should be a well-planned activity. configuration file, such as START OBSERVING, Since a fast-start failover (automatic failover) could become a false failover when the observer or the standby database cannot connect to the primary database within a specific time, which may cost the database to lose some transactions followed by reinstating or recreating the standby database (the former primary database). This list describes restrictions when fast-start failover is enabled. You can upgrade the protection mode later, if necessary, as described in Setting the Protection Mode for Your Configuration. specified, the file is stored in an appropriate directory under the broker's The command fails if the file does not exist. By choosing the standby database with the least amount of unapplied redo, you can minimize the overall time it takes to complete the switchover operation. usually within three seconds if fast-start failover is enabled. All physical and snapshot standby databases will be disabled and must be re-created from a copy of the new primary database after a switchover to a logical standby database. 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. failover to the target standby database. Is possible if the target standby database displays SYNCHRONIZED and the FS_FAILOVER_OBSERVER_PRESENT column displays YES. Fast-start failover will not be attempted for the other types of database shutdown (NORMAL, IMMEDIATE, TRANSACTIONAL). It doesn't consider how much of that redo has been applied. To perform specified actions before or after a fast-start failover time specified in the WAIT option. Twitter:https://twitter.com/hariprasathdba, In Observer sites monitor the fast-start failover environment. The other configurations that are not required but they might make your fast-start failover go smoothly. All standbys other than the failover target are considered bystanders (v$database.fs_failover_status = 'BYSTANDER'). Verify Before Switch-over: If Flashback Database fails, automatic reinstatement stops and you will have to perform a manual SCN-based recovery to the standby_became_primary_scn and complete the reinstatement. When enabling fast-start failover, the broker verifies that the property indicates an existing standby. To optimize the log apply rate: Do not configure the DelayMins database property to delay applying archived redo log files to the standby database (see Managing Log Apply Services for more information). fsfo_postcallout are stored in the same location as Oracle recommends that this property be set to a value that is small enough to allow timely detection of faults at the primary database, but large enough to limit the overhead associated with periodic observer connections to an acceptable level. standby database is mounted, broker remembers this setting. If the former physical standby database was running with real-time query enabled, the new physical standby database will run with real-time query enabled. If the standby database is not enabled for management by the broker, then the failover cannot occur. For example: Using DGMGRL, you can do this by examining the output of the SHOW CONFIGURATION LAG. A failover to a physical standby database is preferable because it is likely that all standby databases in the configuration will still be available as standby databases to the new primary database after the failover operation completes. Data Guard broker publishes this service on each instance as it comes up and broker management of the instance is initialized: To patch an environment where the Observer is running and fast-start failover is enabled, follow these steps prior to applying the patch. To start an observer, you must be able to log in to DGMGRL with an account that has It's a good idea to have at least two hosts configured to run observers so that one can take over if the other fails. You can use Cloud Control or DGMGRL, to perform either a complete (recommended) or an immediate failover. 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. For reliable startup, the initial connection should always be made to the primary. Determining a Database's Readiness to Change Roles. Reinstatement of the failed primary database as a new standby database failed. (Note that the target standby cannot be a far-sync instance. See Directing a Fast-Start Failover From an Application). stored in the specified path using the default file names. After the restart, Redo Apply begins applying redo data from the new primary If the status is SUCCESS, you're ready to start testing role transitions. The broker reinstates a failed primary database as a standby database of the same type (physical or logical standby database) as the old standby database. the observer on ob2-host to become the master Any broker configuration name that is referred to must exist in the configuration declaration section. 4. FSFO can also be used with logical standbys and an FSFO-enabled configuration may have multiple standbys with a mix of physical and logical, but only one standby can be the failover target at any given time. Oracle Database PL/SQL Packages and Types Reference for more information about the DBMS_DG package. Reinstatement is supported only after failover in a broker configuration. The failed primary database requires reinstatement as a new standby database to the new primary. fsfo_hostname.dat. SQL> Select Database_role from v$Database; Subsequent changes to the same block during the same snapshot are not recorded. On primary database NORTH, execute the following: On standby database SOUTH, execute the following: Services that are to be active while the database is in the physical standby role must also be created and started on the current primary database regardless of whether the service will be started on that database or not. STOP OBSERVING, and SET The primary and target standby must have connectivity for the STOP OBSERVER command to complete successfully. The broker selects a target based on the order in which they are specified on the FaststartFailoverTarget property. On Windows, the directory specified by the DG_ADMIN failover configuration file, this script is run. Determine the number and size of the Online Redo Log files (ORLs). The following sections describe how to reinstate or reenable a database. Immediately after issuing command in step 2, shut down and restart the former primary instance PRIM: computer, it automatically starts the observer when you enable Broker will verify that the configuration meets all prerequisites before enabling FSFO and will report any problems it finds. configuration named ConfigurationSimpleName. If the configuration contains both physical and logical standby databases, consider choosing a physical standby database (that has the least amount of unapplied redo) to be the target standby database. START OBSERVING [cfg_group_name] starts a new observer for each broker configuration in the specified group. The following sections provide information about managing observers: How the Observer Maintains Fast-Start Failover Configuration Information, Patching an Environment When the Observer Is Running and Fast-start Failover Is Enabled. The broker preserves the protection mode that was in effect prior to the failover. The connect descriptor must contain the SERVICE_NAME parameter in either case. To protect the files, it's good practice to store them in separate filesystems. environment that is guaranteed to either lose no data (when the See the Cloud Control online help for more information. Application Continuity is supported for Oracle Data Guard switchovers to physical standby databases. If a failure occurs once a reinstatement operation (automatic or manual) is underway, the broker logs the appropriate information in the broker configuration files and broker log files. See the Cloud Control online help for more information. The default value is 30 seconds. Ensure SPFILE is used SQL> sho parameter spfile 2. Sign in to Azure Theoretically, this method can be used when a data guard failover occurred between the primary and standby database, but not a switchover. Fast-start failover quickly and reliably fails over the target standby database to the primary database role, without requiring you to perform any manual steps to invoke the failover. More specifically, we can have an asynchronous second read-only Managed instance in the same or in a different region. The Oracle Database 11g observer can make use of specific credentials, allowing the same wallet to be used for multiple observers with different SYS passwords. Bystanders are part of the Data Guard configuration, but not part of the FSFO configuration. If a group name is not specified, then SHOW OBSERVERS alone is also a valid command. The value specified for either of these properties should allow the master observer to connect to any instance of an Oracle RAC database. Cancel MRP process. See the "DISABLE FAST_START FAILOVER" command in Oracle Data Guard Command-Line Interface Reference for more information. You can use the broker's reinstate capability to make a failed primary database a viable standby database for the new primary. operation. An spfile is required to persist these changes. After a switchover completes, the broker preserves the overall Oracle Data Guard protection mode as part of the switchover process by keeping the protection mode at the same protection level (maximum protection, maximum availability, or maximum performance) it was at before the switchover. For each observer, the V$FS_FAILOVER_OBSERVERS view provides the MASTEROBSERVERHOSTS, DGMGRL reports an error if the For example, perform full level 0 backups weekly and incremental level 1 backups daily. Example 6-2 Sample Observer Configuration File. So if the original Primary database is still accessible, you should always consider a switchover first. You must then re-create it from a copy of the new primary database and reenable it as described in How to Re-create and Reenable a Disabled Database. Note: Data Guard requires dedicated server connections for proper operation. If the protection mode was at maximum availability or maximum performance, it remains unchanged. The state file is locked when the observer is running to prevent multiple observers from using the same file. To avoid problems due to timing variations, values less than 60 minutes are not recommended and values of 30 or less virtually guarantee Flashback Database failure. This section describes how to configure and verify each prerequisite. Now we will see a step-by-step approach to perform a switchover between the primary and the logical standby database: . Steps for FAILOVER the Dataguard environment 1. PDBs. This can be compared to performing an RMAN restore of the datafiles from a backup taken prior to the specified SCN, but is much faster. Note that if failover was performed on a snapshot standby database, the old primary must be either reinstated or re-created as a physical standby database. To allow the master observer to automatically reinstate the former primary database, the database must be started and mounted. The broker first converts the original primary database to run in the standby role. If you intend to switch back to the original primary database relatively soon, you may allow the physical and snapshot standbys to remain disabled. learning with R and Python are also covered in this step-by-step tutorial. By default, both files are stored in $ORACLE_HOME/dbs. If no value is specified for the Duplicate configuration names in configuration definitions are not allowed. Issue the following SRVCTL commands so that both databases in the Data Guard configuration know about the two potential services for each database: To start things up initially, you must manually start the services on the right node. What is true about data guard set up with fast-start failover (FSFO) in Oracle Cloud Infrastructure (OCI)? Such preparation includes: Ensuring that standby redo log files are configured on the primary database. The observer does not attempt to reinstate the former primary database. 1. If the primary database can be mounted, it may be possible to flush any unsent redo data from the primary database to the target standby database using the ALTER SYSTEM FLUSH REDO SQL statement. Otherwise, they must be re-created from a copy of the new primary database. A database in the primary role will not open until it has verified with the observer that it is still the primary. This walkthrough uses Maximum Availability mode to achieve "zero data loss". The database on which the procedure is called notifies the observer. DG_ADMIN environment variable is not set, the files are stored in 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. If you are performing a complete failover, then all accumulated redo data is applied before the database role is changed to primary. In such a case, no attempt is made to transmit any unsent redo from the cascader to the terminal standby. Improper Oracle Net configuration is a leading cause of reported FSFO issues. ConfigurationSimpleName is created. broker does not allow the primary database to commit transactions until it has regained Multiplexing SRLs merely adds unnecessary IO and can increase commit latency. The configuration and database status report that the observer is not running and return one of the following status messages: While the configuration is in the unobserved state, fast-start failover cannot happen. The new primary database is opened in read/write mode and redo transport services are started. PRIM>connect /@PRIM as sysdba The SRVCTL utility does not automatically take the database role into account, so any time you start a service manually, you must specify the name(s) of the service you want started. This file 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. The observe-only mode for fast-start failover enables you to test how fast-start failover will work in your environment. distance. Stopping a Specific Observer When There are Multiple Observers. A single-instance database must be registered with Oracle Restart in order to publish FAN events via ONS. If the switchover transitions a logical standby database to the primary role, then: The original primary database will be switched to a logical standby role. In a complete failover, it is also possible to failover to a standby database (terminal standby) that gets redo from another standby database (cascader). If you want the broker to skip this viability check of bystander standby databases during a complete failover, thus decreasing the overall failover time, set the BystandersFollowRoleChange configuration property to NONE. Initiate the switchover on the primary database PRIM: upheld. 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. This property cannot be used to prevent the primary database from shutting down if a fast-start failover occurred because a user configuration condition was detected or was requested by an application by calling the DBMS_DG.INITIATE_FS_FAILOVER function. 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. If the currently configured mode is maximum protection, Cloud Control will downgrade the mode to maximum availability. The commands that can be executed for a group of configurations (as declared in an observer configuration file) are as follows. The 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. A simple example for *nix is provided below that will work with both releases. The physical and snapshot standby databases will have to be re-created from a copy of the new primary database. Commands For Managing Observers on Multiple Configurations. Note the use of "/@" to login using the wallet. commands. Log in as a test user and make some changes that won't impact other parts of the system. This allows the appropriate Data Guard services, such as redo transport or redo apply, to be started when the database is restarted later for any reason. property. If the client uses remote ONS subscription, the client must specify the hostname and port of the ONS daemon(s) of the primary database and each standby database. SQL>ALTER SYSTEM SWITCH LOGFILE; The primary database, it attempts to disable fast-start failover on as many databases in the configuration with which it has a network connection. ConfigurationSimpleName. If you do not want to use the default, you can define a specific group. You can also specify a list of ORA- errors that will initiate FSFO failover. A running observer will follow the primary automatically after a role transition, but a newly (re)started observer won't start if the initial connection is to a down database or one with an out of date or corrupted Broker config file. configuration. The following steps all require the database to be in a mounted (not open) state. 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". Event notification and database connection failover support is available to database clients connected to local database services when a broker-managed failover occurs. Reinstate or re-create standby databases in the configuration that were disabled by the broker. Displays when the primary and target standby databases are synchronized and the configuration is operating in maximum availability mode. 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. If the primary and target standby databases do not have network connectivity or if the database to which you are connected does not have network connectivity with the primary database, consider using DISABLE FAST_START FAILOVER with the FORCE option. There is no need to multiplex SRLs in order to protect redo as with ORLs (the redo is already protected in the ORLs of the primary). A value of TRUE helps to ensure that an isolated primary database cannot satisfy user queries. The following paragraphs describe the supported availability modes. In this case, disable fast-start failover using the FORCE option on the target standby database. If this is an Oracle RAC physical standby database managed by Oracle Clusterware, then the broker directs Oracle Clusterware to restart the new standby database. These are the actions the broker performs after you start a switchover. After setting local_listener, register the database with the listener and verify the services have been registered. Upon detecting the break in communication, the observer attempts to reestablish a connection with the primary database for the amount of time defined by the FastStartFailoverThreshold property before initiating a fast-start failover.

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