By default, the observer uses the same connect identifiers used by Data Guard for redo transfer and information exchange between the primary and standby ( DGConnectIdentifier in Oracle Database 11g, InitialConnectIdentifier in Oracle Database 10g). Figure 6-2 shows the observer monitoring a fast-start failover configuration. Updates the broker configuration file to record the change in roles. In addition, some standby databases may be disabled by the broker during the failover if the broker detects that they have applied redo beyond where the new primary database had applied. The FastStartFailoverLagLimit configuration property is only used by the broker when enabling fast-start failover for configurations operating in maximum performance mode. 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). contains important information about the observer. observer computer is returned to you so that you can continue to FAN server-side callouts can be configured on the database tier. For Maximum Availability environments, change this to synchronous. automatic failover feature in configurations set up for zero data loss protection at any Start the Data Guard listener on both "a" and "b" hosts. When a serious condition uniquely known to an application is detected, the application can call the DBMS_DG.INITIATE_FS_FAILOVER function to initiate an immediate fast-start failover. Note: this state also occurs on the primary during startup when fast-start failover is possible and neither the target standby database nor the observer are present to confirm it is okay to continue opening the database. If it reconnects to the primary database before the standby agrees to fail over, then the master observer will stop attempting to initiate a fast-start failover. During the failover to the physical standby database, the Oracle 11g DGB performs the following steps: First, it validates that the target standby database is ready to accept the primary role. Switchover and Manual Failover for more information about switchovers and manual failovers, respectively. It is also supported for fast-start failover to physical standbys in maximum availability data protection mode. If failover is not possible for some reason, then the master observer will continue checking whether the standby database is ready to fail over. only. 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. 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. 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". See Setting the Protection Mode for Your Configuration. In this case, Flashback Database cannot be used to reinstate databases. It provides a way to quickly restore a database to a previous point in time or SCN using on-disk data structures called flashback logs. Starting the Observer as a Background Process Using Oracle Database PL/SQL Packages and Types Reference, Stop the observer from any computer system in the broker configuration, as described in, Start the observer on the new computer system, as described in Step 8 of, Enable fast-start failover using the DGMGRL, Shut down the primary database and the target standby database using either DGMGRL, Oracle Database Global Data Services Concepts and Administration Guide, Oracle Real Application Clusters Administration and Deployment Guide, Configure the connect descriptor for connect-time failover. operation: Example 6-1 Fast-start Failover Configuration It's secondary job is to automatically reinstate a failed primary as a standby if that feature is enabled (the default). If groups are not defined, you can still operate on all configurations defined in the file as a whole. In the following example, a service named sales is configured to be active in the PHYSICAL_STANDBY role on the primary database NORTH. standby database, host, or network failure, etc.). Broker Configuration Has Only One Registered Observer. The primary and target standby must have connectivity for the STOP OBSERVER command to complete successfully. A switchover is a role reversal between the primary database and one of its standby databases. configuration file, such as START OBSERVING, 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. Whether or not standby databases that were not the target of failover (bystander standby databases) are disabled depends upon how much redo data they have applied relative to the failover target and the standby type of the failover target: If the failover target is a physical or snapshot standby database, the original primary database must be reinstated or re-created in order to be a standby database for the new primary database. Using Shared Server (MTS) or connection pooling can result in unpredictable behavior. The subcommands for this verb include start, stop, setMaster, show, and delete_alternate_observer. So SALESRW will start on CHICAGO (which is now the primary) and SALESRO will start on BOSTON (which is now the physical standby). This page will not allow you to alter the protection mode. While not strictly required, creating a wallet provides a secure way to store the credentials needed to automatically connect to the primary when starting the observer. You can also switch the master observer hosts for a group of configurations to one specific host. Each observer has its own log file. SWITCHOVER command, and the databases are managed by Oracle Oracle Database 11g observers are incompatible with 10g databases and vice-versa. Goal. If there are physical or snapshot standby databases in the configuration and the switchover occurs to a logical standby database, you need to re-create those databases from a copy of the new primary database and then reenable those databases, as described in Reenabling Disabled Databases After a Role Change. Stopping the observer does not disable fast-start failover. Apply services on all other bystander standby databases automatically begin applying redo data received from the new primary database. To configure fast-start failover in observe-only mode: Fast-start failover will not be triggered if the primary or standby database is shut down normally. 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. Getting the Oracle Net configuration right is one of the key factors in a successful FSFO deployment. change tracking enabled, broker enables block change tracking on the new It is then configured to be active in the PHYSICAL_STANDBY role on the physical standby database SOUTH. post-callout script, and pre-callout success file for the broker The string "NONAME" cannot be used as an observer name. isolated. Performing failover : Step 1: Check Standby Database role. If multiple observers have been started for the configuration, then be sure to specify the name of the observer whose environment is to be patched (STOP OBSERVER observer-name). Presetting database properties related to redo transport services, such as LogXptMode, NetTimeout, StandbyArchiveLocation, StandbyAlternateLocation, and RedoRoutes. If it exists, and it contains a pre-callout script location, If you are performing an immediate failover, then the database role is changed to primary without applying any accumulated redo data. 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. 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. The ObserverPingInterval cannot use a different name for this file. committing because a fast-start failover may have occurred while it was The guide attempts to be operating system agnostic; however, some examples may contain platform specific elements such as path and file naming conventions. To allow the database to register with the Data Guard listener, the listener endpoint must be added to the database's local_listener parameter. Examine the Broker configuration by logging into dgmgrl on the new primary. commands. The example below takes advantage of the 11g RMAN Active Database Duplication feature. Disable fast-start failover using the DGMGRL DISABLE FAST_START FAILOVER command. You enabling fast-start failover. database (if real-time query is enabled). To help you select an appropriate switchover or failover target, use the following DGMGRL commands which perform checks on the database to determine its readiness to complete a role change. You can enable fast-start failover from any site while connected to any database in the broker configuration. All other registered observers are considered to be backup observers. 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. It wouldn't be much of a test if we didn't verify that our durability constraints were being met, so let's make a change on the primary and see if it survives the failover. An observer is an OCI Careful consideration should be given before enabling fast-start failover for either of these conditions because doing so will supersede availability options provided by Oracle Clusterware. 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. Note that primary and standby databases must be licensed for Oracle RAC or Oracle Active Data Guard in order to use Application Continuity. 4. When the standby becomes available again, the primary and standby re-synchronize and resume synchronous redo transfer. To run an observer as a background process, use the DGMGRL command START OBSERVER IN BACKGROUND. During failover, bystanders "follow" the primary by default, flashing back and reapplying redo from the new primary as necessary. 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. 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 What is true about data guard set up with fast-start failover (FSFO) in Oracle Cloud Infrastructure (OCI)? under the $DG_ADMIN directory. 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). directory specified by this variable does not exist, or the directory does not have the time specified in the WAIT option. Ensure SPFILE is used SQL> sho parameter spfile 2. 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. configuration file Errors occurring for any other configuration members will not impede the switchover. Create a trigger based on the, Oracle Database PL/SQL Language Reference, Choosing a Target Standby Database for Switchover, Choosing a Target Standby Database for Failover, Scenario 9: Performing a Switchover Operation, Scenario 10: Performing a Manual Failover Operation, Database Service Configuration Requirements, Troubleshooting Problems During a Switchover Operation, How the Broker Performs a Complete Failover Operation, How the Broker Performs an Immediate Failover Operation, Setting the Protection Mode for Your Configuration, Scenario 7: Enabling Fast-Start Failover When a Far Sync Instance Is In Use, Description of "Figure 6-1 Relationship of Primary and Standby Databases and the Observer", Enabling Fast-Start Failover Task 7: Configure Actions Before and After Fast-start Failover (Optional), Directing a Fast-Start Failover From an Application, Fast-start Failover Callout Configuration Files, Oracle Data Guard Command-Line Interface Reference, Description of "Figure 6-2 The Observer in the Fast-Start Failover Environment", Oracle Enterprise Manager Command Line Interface. Any broker configuration name that is referred to must exist in the configuration declaration section. To enable fast-start failover with DGMGRL, issue the ENABLE FAST_START FAILOVER command while connected to any database in the broker configuration, including on the observer computer. There can be up to four observers for a single Data Guard configuration. you need to make the primary database available, first confirm that a If errors occur during the disable operation, the broker returns an error message and stops the disable operation. (as it might in maximum availability and maximum performance modes). As shown in the table, fast-start failover can be enabled in maximum availability A switchover guarantees no data loss and is typically done for planned maintenance of the primary system. You can issue a Duplicate configuration names in configuration definitions are not allowed. 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. When performing a switchover in a configuration whose standby databases are If a non-zero value is specified for the You can also specify a list of ORA- errors that will initiate FSFO failover. (For example, if the DBMS_LOGSTDBY.SKIP procedure was used to specify which database operations done on the primary database will not be applied to the logical standby database.). 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). Do not use Shared Server (formerly MTS) for Data Guard. These are the guidelines for choosing a target standby database. Always try to perform a complete failover first unless redo apply has stopped at the failover target due to an ORA-752 or ORA-600 [3020] error. Switch-over steps: Step-A: Shutdown primary database: SQL> shut immediate; Database closed. The My Oracle Support note 1625597.1 at http://support.oracle.com for information about compatibility requirements between the observer and DGMGRL, Starting Multiple Observers on a Data Guard Broker Configuration. Such preparation includes: Ensuring that standby redo log files are configured on the primary 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. It also requires Flashback Database to be enabled on both the primary and target standby databases. 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. See Reenabling Disabled Databases After a Role Change for more information. If all the databases do not have the same values, SRVCTL attempts to override the values, which will fail on the physical standby database because it is open read-only. 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. Determines whether or not any standby databases that did not participate in the failover operation have applied redo data beyond the new primary database, and thus need to be disabled. In addition, the primary database will shut down if it perceives a loss of connectivity for a period longer than FastStartFailoverThreshold seconds, if the FastStartFailoverPmyShutdown configuration property is set to TRUE. Initiate the switchover on the primary database PRIM: In the event of a 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. 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. Thus, the command-line prompt on the observer computer does not When the conditions for fast-start failover are met, the Broker adds messages to the observer log and broker log indicating that fast-start failover would have been initiated. In maximum protection mode, an automatic failover is always possible because the 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. If there is more than one registered observer, then this command returns an error; a name is required if there is more than one observer. Use the callout configuration file and script If fast-start failover is enabled, then a switchover can be performed only to the pre-specified target standby database and only if the standby database is synchronized with the primary database or is within the configured lag limit, for the max availability and max performance modes respectively. So if the original Primary database is still accessible, you should always consider a switchover first. $DG_ADMIN/config_ConfigurationSimpleName/callout You can use Cloud Control or DGMGRL, to perform either a complete (recommended) or an immediate failover. Syntax for Mandatory Configuration Declaration. In order for Flashback Database to succeed, there must be sufficient history available in the Flashback Database logs and all of the redo generated between the restore point and the standby_became_primary_scn must be available. The following steps all require the database to be in a mounted (not open) state. It has two parts in the following order: Configuration declaration this section is mandatory. Complete Failovers in Configurations Using Far Sync Instances. file, observer runtime data file (fsfo.dat), fast-start failover callout The following list indicates the extent to which fast-start failover is disabled in the broker configuration when the DISABLE FAST_START FAILOVER FORCE command is issued on the primary database, target standby database, and a standby database that is not the fast-start failover target. Oracle Data Guard 11gr2 Administration Beginner S Guide As recognized, adventure as well as experience practically lesson, amusement, . If the protection mode was at maximum protection, it is reset to maximum performance. To proceed, you must first disable fast-start failover using the FORCE option, and then perform a manual failover. Cloud Control will start the observer. Otherwise, they must be re-created from a copy of the new primary database. become the master observer. Data Guard uses Oracle Net (SQL*Net) for communication between the primary and standby databases and the FSFO observer. It is possible to manually perform a completer failover to a standby database that receives redo data from a far sync instance. The master observer cannot connect to the target standby database, What Happens if the Observer Fails? This is typically done for planned maintenance of the primary system. 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. ObserverConfigFile is a DGMGRL session runtime property. Clusterware: The broker notifies Oracle Clusterware to stop active This function can be called from a connection to either the primary or any standby in the configuration. For this build, we will use a single physical standby database. If client-side ONS configuration is used, the client-side ONS configuration file must specify the hostname and port of the ONS daemon(s) of the primary database and each standby database. lose no more than the amount of data (in seconds) specified by the The broker controls the rest of the switchover. Some of the statistics that can be monitored are as follows: LAST_FAILOVER_TIME that shows the timestamp of last fast-start failover, LAST_FAILOVER_REASON that shows the reason for the last fast-start failover. The following paragraphs describe the supported availability modes. observer on ob1-host will be given priority over milliseconds and that of ObserverRetryCount is 10. Written by authors well-known for their talent with RAC, Pro Oracle Database 11g RAC on Linux . SHOW CONFIGURATION VERBOSE, or SHOW OBSERVER A single-instance database must be registered with Oracle Restart in order to publish FAN events via ONS. SET ObserverConfigFile used to specify a customized observer configuration file. The connect descriptor can be configured in one of two ways: Oracle Database PL/SQL Language Reference for more information about the DB_ROLE_CHANGE system event. Database hosts are referred to as "a" and "b" hosts and the databases themselves are referred to as the "a" and "b" databases. If fast-start failover is enabled you can still perform a switchover or a manual failover as long as certain conditions are met. 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. That is, if the observer is connected to any instance in the Oracle RAC, all instances will show a value of YES. primary, only the observers specified in the property can be use in the SET The name of the callout configuration file is fsfocallout.ora. 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. Setting this property to 'TRUE' (the default) causes the primary to self-terminate. Once the observer is started, you cannot change the file's name and location. To do this, use the SET ObserverConfigFile and SHOW ObserverConfigFile commands. services. In such a case, no attempt is made to transmit any unsent redo from the cascader to the terminal standby. The following example displays the contents of the fast-start failover Credentials Required for Access to Broker Configurations. The procedure for using RMAN to create a standby database is fully explained in Appendix F of Oracle Oracle Data Guard Concepts and Administration document (10g Rel 2 and 11g Rel 1). Flashing back a database is much faster and more seamless (one simple DDL statement) than traditional point-in-time or SCN-based recovery. Subsequent changes to the same block during the same snapshot are not recorded. Immediately after issuing command in step 2, shut down and restart the standby instance STAN: Once the primary database regains connectivity with the target standby database, fast-start failover will be disabled for all the databases in the configuration. You can manage observers through either the Oracle Data Guard Overview pages in Cloud Control or using DGMGRL commands. configuration named ConfigurationSimpleName. Note that if the V$DATABASE.FS_FAILOVER_STATUS column has a value of DISABLED, then any values returned for the remaining columns related to fast-start failover (V$DATABASE.FS_FAILOVER_*) become irrelevant. If you will be using RMAN to create the standby database, it also needs a static service to restart the database being created. (Snapshot standbys are not included in the table because they are not supported as fast-start failover targets.). You must ensure that the primary database is shut down prior to performing a manual failover. In maximum performance mode, the ability to automatically failover is restored (Oracle Call Interface) client that connects to the primary and target standby databases Set both these properties to achieve a primary failure detection time of 1 PDBs. However, there may be exceptions to the recommendation to choose a physical standby database as the target standby database. It is not reversible. A switchover guarantees no data loss and is typically done for planned maintenance of the primary system. Each database in a Data Guard configuration must have a unique name. After setting local_listener, register the database with the listener and verify the services have been registered. Oracle Database PL/SQL Packages and Types Reference for more information about the DBMS_DG package. See the START OBSERVER
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