Broker is a Data Guard management utility that maintains state information about a primary and its standby databases. operation can be automated using callout scripts. Steps for FAILOVER the Dataguard environment 1. (Snapshot standbys are not included in the table because they are not supported as fast-start failover targets.). standby database is mounted, broker remembers this setting. fast-start failover operation, the observer checks if a fast-start failover Tags: Data Guard, Oracle. Oracle Data Guard can switch a standby database to the primary role in case a production database becomes unavailable due to . 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. 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. For Active Oracle Data Guard, it will fail to open up a connection unless its in read-only mode. VALIDATE Perform a switchover to a standby database that is not configured as the fast-start failover target, Perform a switchover to the target standby database in a configuration operating in maximum availability mode, unless the standby database is synchronized with the primary database, Perform a switchover to the target standby database in a configuration operating in maximum performance mode, unless the standby database is within the lag limit of the primary database. The failover was to a logical standby database. 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. The observer is the third party in an otherwise typical primary/standby Data Guard configuration. The failover time is dependent upon whether the target standby database (physical or logical standby database) has applied all of the redo data it has received from the primary database. To perform specified actions before or after a fast-start failover ASYNC. The observer is very lightweight, requiring few system resources. However, if you want the observer to reconnect to the primary database periodically as a means of testing the health of the network connection to the primary, then use the ObserverReconnect configuration property. The broker allows the switchover to proceed as long as there are no errors for the primary database and the standby database that you selected to participate in the switchover operation. Oracle Data Guard 11gr2 Administration Beginner S Guide As recognized, adventure as well as experience practically lesson, amusement, . However, fast-start failover cannot occur when the target standby database is in an unobserved state. If the configured data loss guarantee cannot be upheld, the current working directory. It has two parts in the following order: Configuration declaration this section is mandatory. 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. If reinstatement of a database fails, its status changes to ORA-16795: the standby database needs to be re-created. Use synonyms for the keyword you typed, for example, try "application" instead of "software.". The configuration must be operating in either maximum availability mode or maximum performance mode in order to be able to switch over to a logical standby database. For systems with multiple RAID controllers, consider creating SRLs such that their IO is balanced across the controllers. As mentioned above, Maximum Availability mode is mandatory for Oracle Database 10g and optional for Oracle Database 11g. Unlike the primary / standby interconnect, where bandwidth and latency are determining performance factors, the observer requires very little network bandwidth and is not overly latency sensitive, allowing the it to be placed practically anywhere a reliable connection is available. Note: the FSFO observer version must match the database version. What is true about data guard set up with fast-start failover (FSFO) in Oracle Cloud Infrastructure (OCI)? If the switchover occurs to a physical standby database, and the former primary Group definition this section is optional. You can manually stop a specific observer or all observers. In the restore stage, Flashback Database restores the database to a point prior to the standby_became_primary_scn using the before-image blocks in the Flashback Database logs. You must ensure that the primary database is shut down prior to performing a manual failover. To restore your original disaster-recovery solution after switchover to a logical standby database or after failover to any standby database, you may need to perform additional steps. 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. Note that the broker does not use the properties to set up redo transport services and Redo Apply services until you actually switch over the primary database to the standby role. In the event of a Determine the number and size of the Online Redo Log files (ORLs). Broker maintains these parameters by issuing ALTER SYSTEM commands as appropriate during role transitions, database startup/shutdown, and other events. Disabling Fast-Start Failover Using DGMGRL. A database in the primary role will not open until it has verified with the observer that it is still the primary. Choosing the standby database with the smallest transport lag can minimize the amount of data loss and in some cases, incur no data loss at all. The FS_FAILOVER_OBSERVER_PRESENT column, which indicates whether the observer is running and actively pinging the database. DGMGRL> show configuration Configuration - CDB01_fraad1_CDB01_fraad3 Protection Mode: MaxAvailability Members: CDB01_fraad1 - Primary database CDB01_fraad3 - (*) Physical standby database 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. 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. File. The FS_FAILOVER_STATUS column in the V$DATABASE view for the target standby database displays a reason why fast-start failover cannot occur. Oracle Data Guard with Fast-Start Failover (FSFO) can provide additional resiliency by setting up the broker on a separate machine. 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. Reinstatement of the failed primary database as a new standby database failed. The new primary database starts transmitting redo data to the new standby database. time specified in the WAIT option. If you will be using RMAN to create the standby database, it also needs a static service to restart the database being created. Database hosts are referred to as "a" and "b" hosts and the databases themselves are referred to as the "a" and "b" databases. This may result in data loss. It automatically recovers the maximum amount of redo data for the protection mode the configuration is operating in. observer on ob1-host will be given priority over To prevent automatic reinstatement of the former primary database in these cases, set this configuration property to FALSE. instructions for the DGMGRL command-line interface. Step-B: Copy control file to temporary location on primary database. This configuration property causes the former primary database to be automatically reinstated if a fast-start failover was initiated because the primary database was either isolated or had crashed. These Immediately after issuing command in step 2, shut down and restart the standby instance STAN: In this mode, the FastStartFailoverLagLimit configuration property is set to zero. In This not only saves time and minimizes problems by automating an otherwise manual process, it exercises your failover and DR procedures with every flip so that you know the FSFO configuration is sound and, in a real emergency, everyone knows what to do. STAN is now transitioned to the primary database role.Now your PHYSICAL STANDBY Database has become PRIMARY. 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. This walkthrough uses Maximum Availability mode to achieve "zero data loss". Issue the following command while connected to any database in the broker configuration, except the database that is to be reinstated: The newly reinstated standby database will begin serving as a standby database to the new primary database. To issue commands and interact with the See Reenabling Disabled Databases After a Role Change for more information. 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. The minimum detection time is 6 seconds, which is the default See Sources of Diagnostic Information for details about the broker's drc* log files. 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. For reliable startup, the initial connection should always be made to the primary. Reinstating the Former Primary Database in the Broker Configuration for more information about reinstatement. It may be possible to convert the old Primary into a Standby database now instead of having to do a time consuming duplicate again. It is not reversible. specified by the ObserverPingInterval property. Then the STOP OBSERVER command can be issued successfully on the former master observer. If you re-create the old primary database, it must be created as the standby type of the old standby database. Please contact us at contactus@smarttechways.com. These tasks assume that you are connected as SYS or SYSDG and that a primary and standby database are already set up in a broker configuration. post-callout script, and pre-callout success file for the broker You can switch back to the original primary and then either retry the switchover to the original target standby, or choose another standby in the configuration to switch over to. 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. It doesn't consider how much of that redo has been applied. Conditions shown in blue are enabled by default. The real test of the configuration is a successful role transition in both directions with both switchover and FSFO failover. Tasks that must be performed before and after a fast-start failover The walkthrough begins with a single database that will become the primary of a Data Guard configuration. Suppose you have a primary database, BOSTON, and a standby database, CHICAGO. 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. Database services can be configured to be active in specific database roles on Oracle RAC databases and on single-instance databases managed by Oracle Restart. They can all be done at the same time in a single bounce. You can query the V$FS_FAILOVER_STATS view on the primary database to display statistics about fast-start failovers that have occurred on the system. Each group that you define must have at least one broker configuration. For manual failover, the observer is started and communicating with the target standby database. 2. Figure 6-2 shows the observer monitoring a fast-start failover configuration. Note that enabling FSFO does not make the configuration ready for automatic failover - that requires an observer, which we'll get to next. Note: Data Guard requires dedicated server connections for proper operation. 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. When fast-start failover is enabled, the primary and standby randomly choose one of the registered observers to be the master. FastStartFailoverLagLimit configuration property is set to zero) or In order to fully automate switchover, Broker needs SYSDBA credentials in order to restart one or both databases. The minimum allowable limit is 10 seconds. The broker allows an immediate failover to proceed even if there are errors present on the standby database that you selected to participate in the failover. However, the event notifying a failover is only published for database services that have been configured to be active while the database is in the primary role on the new primary database. 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. In addition, the database to be reinstated and the new North_Sales is in the primary role. LGWR is unable to write to any member of the log group because on an I/O error. A failed ping is a ping to Automatic failover quickly and reliably fails over the standby Autonomous database to the primary database role, without requiring you to perform any manual steps. 1. time specified by maximum configured These are the guidelines for choosing a target standby database. 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. Once you set these properties, their values persist through role changes during switchover and failover. Flashing back a database is much faster and more seamless (one simple DDL statement) than traditional point-in-time or SCN-based recovery. Instead, when broker notifies the Oracle In short, the failover is the deformation of the production (primary) database and activating standby database as the primary. Setting it to 'FALSE' leaves the database open and stalled until it is terminated or signaled to proceed in the event a failover did not take place (e.g. When both databases have been restarted, you may restart the observer. By default, a fast-start failover is done when both the observer and the standby cannot reach the primary after the configured time threshold (FastStartFailoverThreshold) has passed. The reduced need for manual intervention can increase availability without increasing management costs. Provides an automatic failover environment that SQL>ALTER SYSTEM SWITCH LOGFILE; The name of the callout configuration scripts is specified in To see if your primary has already met a prerequisite, follow the instructions in the Verify section. If you don't already have a Flash Recovery Area (FRA), you will need to create one for Flashback Database. Stopping the observer does not disable fast-start failover. Alternatively, you can query the V$DATABASE view on the target standby database. If the observer is stopped abnormally (for example, by typing CTRL/C), restart it and reference the existing fsfo.dat file with the FILE IS qualifier. 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. 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. These facilities allow applications written to take advantage of them to receive asynchronous notification of database events, including role transitions. The primary database was shut down without using the ABORT option. Bystander standby databases can be shut down at any time in any order without impacting fast-start failover. If the target is a snapshot standby database, the broker first converts the database back to a physical standby and then starts Redo Apply to apply all the accumulated redo before completing the failover and opening the database as a primary database. session. Data guard Configuration details:- Login in to Standby Server:- Step:1 Check the database role and open_mode Select name,open_mode,database_role from v$database; Fast-start failover will not be attempted for the other types of database shutdown (NORMAL, IMMEDIATE, TRANSACTIONAL). The broker never automatically reinstates the former primary database if a fast-start failover was initiated because a user configuration condition was detected or was requested by an application calling the DBMS_DG.INITIATE_FS_FAILOVER function. 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. Note: Many of the Broker database properties correspond to database spfile parameters. Standby databases that are disabled during switchover, manual failover, or fast-start failover will not be automatically reinstated. Complete Failovers in Configurations Using Far Sync Instances. The "Configuring Authentication" chapter of the Oracle Database Security Guide provides detailed instructions for creating a wallet. gets enabled and then begins monitoring. 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 same thing happens if a shutdown and startup of either database occurs - the service that is started is the one that matches the role of the database being started. For Oracle Database Release 12.2 and higher, Oracle Enterprise Manager Cloud Control (Cloud Control) supports configuring multiple observers using the Enterprise Manager Command Line Interface (EM CLI). Then, on the Failover Confirmation page, click Yes to invoke the default Complete failover option. Configure the protection mode. 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. Instead, the old primary database must be re-created as a standby from a backup of the new primary using the procedure described in How to Re-create and Reenable a Disabled Database. The following example shows you how to set up more than one service on a database and how using the broker ensures that the correct service starts on the correct database. They must be re-created from a copy of the new primary database. This page will not allow you to alter the protection mode. Create a script to automate FSFO failover initiation and use it as your standard method for standby flips. They cannot be reinstated. When performing a switchover in a configuration whose standby databases are Verify there are no active users connected to the databases. Contains the observer runtime data file for the broker The Data Guard broker and the secondary database both run the observer and observe the primary database for downtime. This property specifies the amount of data, in seconds, that the target standby database can lag behind the primary database in terms of redo applied. irrespective of its content, indicates that the script executed successfully. The former primary database is disabled. Fast-start failover will not occur unless all instances comprising the Oracle RAC primary database are perceived to have failed. disable fast-start failover with the FORCE option on the In these sample commands, the ellipse () signifies any other add service options you wish to supply. The default name of the observer runtime data file is Broker stores it configuration information in a mirrored set of files outside the database. The broker may not be able to disable fast-start failover on all databases in the broker configuration when you issue the DISABLE FAST_START FAILOVER FORCE command. Provides an automatic failover environment Opens the new primary database in read/write mode. configuration property specifies how frequently the observer 1. All standbys other than the failover target are considered bystanders (v$database.fs_failover_status = 'BYSTANDER'). You can also reinstate bystander standby databases that were disabled during a failover operation. process. This feature increases the availability of your database in the event of a disaster by reducing the need for you to perform a failover operation manually. You can switch back to the original Primary database later by performing another switch over. failover configuration file, this script is run. the service configuration. SET ObserverConfigFile used to specify a customized observer configuration file. START OBSERVING [cfg_group_name] starts a new observer for each broker configuration in the specified group. To verify the readiness of the fast-start failover configuration, issue the DGMGRL SHOW CONFIGURATION VERBOSE command or the SHOW FAST_START FAILOVER command on the primary database. Examine the Broker configuration by logging into dgmgrl on the new primary. Attempt to open the primary database, or the following error may be returned: This error may return if the fast-start failover validity check fails or does not complete in under two minutes. Before stopping an observer, note the following: The observer does not stop immediately when you issue the STOP OBSERVER command. failover with the FORCE option on the primary database. first recording that a fast-start failover cannot happen. Verify dmon process is running and broker parameters viz. An spfile is required to persist these changes. the current working directory, Uses standard output for displaying the observer logs. Slightly less critical than making sure you've got a good primary is making sure the failed primary can be automatically reinstated. 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. In order to accommodate all load conditions, Oracle recommends having at least one more SRL group than the number of ORL groups of the same size. SQL>SHUTDOWN IMMEDIATE; They may be reinstated if Flashback Database is enabled on those databases. Regardless of the method you choose, the broker coordinates the role transition on all databases in the configuration. The command SHOW OBSERVER provides detailed information about registered observers. If the PreferredObserverHosts property is set for the current Use the wrapper script to start the observer process when the observer host boots or to restart it if it dies. 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. select name,open_mode,database_role from v$database; Note: Indexing is a mechanism by which the underlying data is mapped for faster retrieval.
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